The essence of the search for the most stable structure is reduced to the calculation of such a state of a substance that has the lowest energy. The energy in this case depends on the electromagnetic interaction of the nuclei and electrons of atoms, of which the crystal studied. It can be estimated with the help of quantum-mechanical calculations based on the simplified Schrödinger equation. So in the USPEX algorithm used theory of density functionalwhich was developed in the second half of the last century. Its main goal is to simplify the calculations of the electronic structure of molecules and crystals. The theory allows you to replace the multielectronic wave function of electronic density, while remaining formally accurate (but in fact the approximation turns out to be inevitable). In practice, this leads to a decrease in the complexity of calculations and, as a result, the time that will be spent on them. Thus, quantum-mechanical calculations are combined with an evolutionary algorithm in USPEX (Fig. 2). How does the evolutionary algorithm work?
It is possible to search for structures with the lowest energy: accidentally position the atoms relative to each other and analyze each such state. But since the number of options is huge (even if atoms are only 10, then the possibilities of their location relative to each other will be about 100 billion), then the calculation would take too much time. Therefore, the success of scientists managed to achieve only after the development of a more cunning method. USPEX algorithm is based on an evolutionary approach (Fig. 2). First, a small number of structures is randomly generated and their energy is calculated. Options with the highest energy, that is, the least stable, the system is removed, and from the most stable generates similar and calculates them. At the same time randomly the computer continues to generate new structures to maintain a diversity of the population, which is an integral condition for successful evolution.
Thus, the problem of predicting crystal structures helped the logic taken from biology. It is difficult to say that there is a gene in this system, because new structures may differ from their predecessors with very different parameters. The most adapted to the selection conditions "individuals" leave offspring, that is, the algorithm, learning to his mistakes, maximizes the chances of success in the next attempt. The system pretty quickly finds a variant with the lowest energy and effectively calculates the situation when the structural unit (cell) contains dozens and even the first hundred atoms, while the previous algorithms could not cope with ten.
One of the new tasks that is placed in front of USPEX in MIPT is the prediction of the tertiary structure of proteins by their amino acid sequence. This problem of modern molecular biology is among the key. In general, before scientists, the task is very difficult also because it is difficult to calculate energy for such a complex molecule as a protein, difficult. According to Artem Oganova, its algorithm is already able to predict the structure of peptides about 40 amino acids.
Video 2. Polymers and biopolymers. What substances relate to polymers? What is the structure of the polymer? How common is the use of polymeric materials? About this says Professor, Phd In Crystallography Artem Oganan.
In one of his scientific and popular artem Oganov (Fig. 3) describes uspex as follows:
"Here is a figurative example for demonstrating a common idea. Imagine that you need to find the highest mountain on the surface of an unknown planet, on which a complete darkness reigns. In order to save resources, it is important to understand that we need not a complete relief map, but only its highest point.
Figure 3. Artem Romaevich Yoganov
You land on the planet a small landing of biorobot, sending them one by one in arbitrary places. The instruction that each robot must perform is to go over the surface against the forces of gravitational attraction and as a result of reaching the tops of the nearest hill, the coordinates of which he must inform the orbital base. We have no funds for a large research contingent, and the likelihood that one of the robots will immediately take the highest mountain, extremely small. Therefore, it is necessary to apply the well-known principle of Russian military science: "Better not by the number, and the ability", implemented herein in the form of an evolutionary approach. The damping of the nearest neighbor, the robots meet and reproduce themselves like this, arranging them along the line between "their" vertices. The offspring of bioreobots proceeds to perform the same instructions: they move towards the elevation of the relief, exploring the region between the two vertices of their "parents". Those "individuals", which came the vertices below the average level, respond (this is being selected) and landing anew randomly (this is simulated maintaining the "genetic diversity" of the population) ".
How to estimate the error with which uspex works? You can take a task with a pre-known correct answer and decide it 100 times with 100 times with the help of an algorithm. If the correct answer is obtained in 99 cases, the probability of the calculation error will be 1%. Typically, the correct predictions are obtained with a probability of 98-99%, when the number of atoms in the elementary cell is 40 pieces.
The USPEX evolutionary algorithm led to many interesting discoveries and even to the development of a new medicinal form of a medical drug, which will be discussed below. I wonder what will be when the new generation supercomputers appear? Will the crystal structural prediction algorithm change? For example, some scientists are engaged in the development of quantum computers. In the future, they will be much more effective than the most advanced modern. According to Artem Oganova, the evolutionary algorithms will leave the leading position, but they will begin to work faster.
Uspex turned out to be an algorithm not only efficient, but also multifunctional. At the moment, under the leadership of Artem Oganova, a lot of scientific papers in various directions are conducted. Some of the latest projects are attempted simulation of new thermoelectric materials and the prediction of the structure of proteins.
"We have several projects, one of them is the study of low-dimensional materials, such as nanoparticles, material surfaces, Another is the study of chemicals under high pressure. There is another interesting project associated with the prediction of new thermoelectric materials. Now we already know that the adaptation of the method for the prediction of the crystal structures, which we invented, the thermoelectric tasks work efficiently. At the moment, we are ready for a large jerk, the result of which the discovery of new thermoelectric materials should be. It is already clear that the method that we created for thermoelectricians is very powerful, the tests spent are successful. And we are fully prepared to search for new materials. We also deal with the prediction and study of new high-temperature superconductors. We ask the question of predicting the structure of proteins. It is a new task for us and very curious. "
Interestingly, USPEX has already benefited even medicine: "Moreover, we are developing new medications. In particular, we were predicted, a new medicine was obtained and patented, - tells A.R. Yogan. - This is a hydrate 4-aminopyridine, a medicine from multiple sclerosis ".
We are talking about the recently patented laboratory of computer design materials by Valery Rosizen (Fig. 4), Anastasia Naumova and Artem Ogana, allowing symptomatically to treat multiple sclerosis. Patent outdoor, which will help reduce the price of the medicine. Scattered sclerosis is a chronic autoimmune disease, that is, one of those pathologies when its own immune system harms the owner. At the same time, the myelin sheath of nerve fibers is damaged, which normally performs an electrically insulating function. It is very important for the normal operation of neurons: the current on the growth of nerve cells covered with myelin is carried out 5-10 times faster than on uncovered. Therefore, multiple sclerosis leads to violations in the work of the nervous system.
The root causes of the occurrence of multiple sclerosis remain completely uncalled. They are trying to understand them in many laboratories in the world. In Russia, this is engaged in the laboratory of biocatalysis at the Institute of Bioorganic Chemistry.
Figure 4. Valery Roizen - one of the authors of a patent for a medicine from sclerosis, An employee of the laboratory of computer design materials, developing new dosage forms of medical drugs and actively engaged in popularizing science.
Video 3. Scientific and popular lecture Valery Rosizen "Delicious crystals". You will learn about the principles of the work of drugs, about the importance of the form of delivering a medicine into the human body and about the evil twin brother aspirin.
Earlier, 4-aminopyridine in the clinic has already been used, but scientists managed to change the chemical composition, improve the absorption of this medication into the blood. They obtained the 4-aminopyridine crystal hydrate (Fig. 5) with stoichiometry 1: 5. In this form, the medicine itself was patented and the method of obtaining it. The substance improves the emission of neurotransmitters in neuromuscular synapses, which facilitates the well-being of patients with multiple sclerosis. It is worth noting that such a mechanism implies the treatment of symptoms, but not the very disease itself. In addition to bioavailability, the principal moment in the new development is the following: since it was possible to "conclude" 4-aminopyridine in the crystal, it became more convenient for use in medicine. Crystalline substances are relatively easy to obtain in purified and homogeneous form, and freedom of the drug from potentially harmful impurities is one of the key criteria for a good medication.
As mentioned above, USPEX allows you to find new chemical structures. It turns out that even the "habitual" carbon has its own riddles. Carbon is a very interesting chemical element, because it forms an extensive set of structures, ranging from superhard dielectrics, ending with soft semiconductors and even superconductors. To the first one can include diamond and lansdalet, to the second - graphite, to the third - some fullerenes at low temperatures. Despite the wide variety of known carbon forms, scientists under the guidance of Artem Oganova managed to open a fundamentally new structure: it was not previously known that carbon can form complexes in the "Guest-owner" type (Fig. 6). The work took part in the work of the Laboratory of Computer Design of Materials (Fig. 7).
Figure 7. Oleg Fairy, graduate student of the MFTI, employee of the laboratory of computer design materials and one of the authors of the open carbon structure. In his free time, Oleg is engaged in popularizing science: his articles can be found in the publications "Cat Schredinger", "For Science", Strf.Ru, "Rosatom". In addition, Oleg - Winner of Moscow Science Slam. And the participant of the TV show "The Smart".
The interaction of the "guest-owner" manifests itself, for example, in complexes consisting of molecules that are connected to non-virulent connections. That is, a certain atom / molecule occupies a certain place in the crystal lattice, but it does not forms a covalent connection with the surrounding compounds. Such behavior is widespread among biological molecules that bind to each other, forming durable and large complexes that perform various functions in our organism. In general, due to the compound consisting of two types of structural elements. For substances formed only by carbon, such forms were not known. Scientists have published their discovery in 2014, expanding our knowledge of the properties and behavior of the 14th group of chemical elements in general (Fig. 8). It is noted that in the open carbon form, covalent bonds are formed between atoms. We are talking about the type of host-owner comes due to the presence of well-pronounced two types of carbon atoms that have a completely different structural environment.
In the laboratory of computer design materials are studied which substances will be stable at high pressures. This is how the head of the laboratory argues interest in such research: "We study materials under high pressure, in particular new chemistry, which appears under such conditions. This is a very unusual chemistry that does not fit into the rules of traditional. The knowledge gained on new connections will lead to an understanding of what happens inside the planets. Because these unusual chemicals can show themselves as very important materials of planetary subsoils. " It is difficult to predict how high-pressure substances behave: most of the chemical rules stop working, because these conditions are very different from usual. Nevertheless, it is necessary to understand this if we want to know how the universe is arranged. The lion's share of the baryon substance of the universe is precisely high pressure inside the planets, stars, satellites. Surprisingly, it is still very few about his chemistry.
New chemistry, which is implemented at high pressure in the Laboratory of Computer Design Materials of MFTI studies PHD (degree similar to Candidate of Science) Gabriele Saleh (Gabriele Saleh):
"I am a chemist, and I am interested in chemistry at high pressures. Why? Because we have the rules of chemistry that have been formulated 100 years ago, but recently it turned out that they cease to work at high pressures. And it is very interesting! Looks like Moon Park: there is a phenomenon that no one can explain; Explore the new phenomenon and try to understand why it is happening - it is very interesting. We started a conversation with fundamental things. But high pressure exists in the real world. Of course, not in this room, but inside the earth and on other planets " .
SINCE I'm A Chemist I'm Interested in High-Pressure Chemistry. Why? BECAUSE WERE CHEMICAL RULES WERE WERE ESTABLISHED ONE HUNDRED YEARS AGO But Recently It Was Discovered That These Rules Get Broken At High Pressure. AND IT IS Very Interesting! This Is Like A LoonoPark Because You Have A Phenomenon, Which Nobody Can Rationalize. IT'S Interesting to Study New Phenomenon and To Try to Understand Why Does It Happen. We started from the Fundamental Point of View. But These High Pressures Exist. NOT IN THIS ROOM OF COURSE BUT IN THE INSIDE OF THE EART AND IN OTHER PLANETS.
Figure 9. Coalic acid (H 2 CO 3) is a stable structure under pressure. In the inset from above It is shown that along axes C. Polymer structures are formed. The study of the carbon-oxygen-hydrogen system under high pressures is very important for understanding how the planets are arranged. H 2 O (Water) and CH 4 (methane) are the main components of some giant planets - for example, neptune and uranium, where pressure can reach hundreds of GPa. Large icy satellites (Gamornad, Callisto, Titan) and comets also contain water, methane and carbon dioxide, which is applied to several GPa.
Gabriele told us about her new job, which was recently accepted for publication:
"Sometimes you are engaged in fundamental science, but then detect a direct application of the knowledge gained. For example, we recently sent an article to publish in which we describe the search results for all stable compounds obtained from carbon, hydrogen and oxygen at high pressure. We found one, stable at very low pressures, such as 1 GPa And they were coalic acid H 2 CO 3 (Fig. 9). I studied astrophysics literature and found that the satellites of Ganymed and Callisto [satellites of Jupiter] consist of water and carbon dioxide: from molecules forming coalic acid. Thus, we realized that our discovery suggests the formation of carbonic acid there. This is what I said: It all started with fundamental science and ended with something important for the study of satellites and planets " .
Note that such pressure turn out to be low on those that, in principle, can be found in the universe, but high compared to those that act on us at the surface of the Earth.
So Sometimes You Study Something for Fundamental Science But Then You Discover It Has a Right Application. For example We Have Just Submitted a Paper in Which We Took Carbon, Hydrogen, Oxygen At High Pressure and We Tried to Look for the All Stable Compounds. We Found One Which Was Carbonic Acid and It Was Stable in a Very Low Pressure Like One Gigapascal. I Investigated The Astrophysics Literature and Discovered: There Are Satellites Such As Ganymede or Calisto. ON THERE IS CARBON DIIXIDE AND WATER. The Molecules Which Form This Carbonic Acid. So We Realized That This Discovery Means That ProBably There Would Be Carbonic Acid. This Is What I Mean by Started for Fundamental and Discovering Something Which is Applicable to Planetary Science.
Another example of unusual chemistry, which can be brought regarding well-known cook salt, NaCl. It turns out that if you can create a 350 GPa pressure in your salt, then you will get new connections. In 2013, under the direction of A.R. Oganova was shown that if it was high pressure to NaCl, the unusual compounds will become stable - for example NaCl 7 (Fig. 10) and Na 3 Cl. Interestingly, many of open substances are metals. Gabiel Saleh and Artem Oganov continued to pioneer work, which showed the exotic behavior of sodium chlorides under high pressure and developed a theoretical model that can be used to predict the properties of alkali metal compounds with halogens.
They described the rules that these substances are subject to such unusual conditions. Using the USPEX algorithm, several compounds with formula A 3 Y (A \u003d Li, Na, k; Y \u003d F, CL, BR) were theoretically pressurized to 350 GPa. This led to the discovery of chloride ions in oxidized state -2. "Standard" chemistry prohibits this. In such conditions, new substances may be formed, for example, with the chemical formula Na 4 Cl 3.
Figure 10. Crystal structure of the NaCl conventional salt ( left) and unusual compound NaCl 7 ( on right), stable under pressure.
Gabriele Saleh (Fig. 11) spoke about his study aimed at a description of the new rules of chemistry, which would have a predictive force not only under standard conditions, but would describe the behavior and properties of substances under high pressure (Fig. 12).
Figure 11. Gabriel Saleh (Gabriele Saleh)
"Two or three years ago, Professor Yoganov discovered that such a simple salt, as NaCl, is not so simple: sodium and chlorine can also form other connections. But no one knew why. Scientists fulfilled the calculations, received results, but remained unknown, why everything happens so, and not otherwise. Since graduate school, I study a chemical connection, and during the study, I managed to formulate some rules, logically explaining what was happening. I studied how electrons behave in such compounds, and came to general laws characteristic of them under high pressure. In order to check whether these rules are the fruit of my imagination or still objectively correctly, I predicted the structure of similar connections - LIBR or NABR and more similar. And indeed - the general rules are followed. If briefly, I saw that there is the following trend: when you apply the pressure to such compounds, then they form the structure of the two-dimensional metal, and then - one-dimensional. Then, under very high pressure, more wild things begin to occur, because chlorine in this case will be the degree of oxidation -2. All chemists know that Chlorine has a degree of oxidation -1, this is a typical example from the textbook: sodium loses the electron, and chlorine takes it. Therefore, oxidative numbers are obtained +1 and -1, respectively. But under high pressure, everything works wrong. We have shown that with the help of some approaches for the analysis of chemical bonds. Also during the work, I was looking for special literature to understand whether anyone was already observed such regularities. And it turned out that yes, watched. If I am not mistaken, sodium bisputat and some other connections are subject to the rules described. Of course, this is just the beginning. When you publish the following works on the topic, we learn whether our model has a real predictive force. Because it is exactly what we are looking for. We want to describe chemical laws that would be respected at high pressures " .
Two Or Three Years Ago Professor Oganov Discovered That The Simple Salt NaCl At High Pressure Is Not Very Simple and Other Compounds Will Form. But Nobody Know Why. They Made A Calculation The Got The Results But You Cannot Say Who This Is Happening. SO SINCE DURING MY PHD I SPECIALIZING IN THE STUDY OF CHEMICAL BONDING, I INVESTIGATED THIS COMPOUNDS AND I FIND SOME RLE TO RATIONALIZE WHAT IS GOING ON. I Investigated How Electrons Behave In This Compounds and Came Up with Some Rules Which This Kinds of Compounds Will Follow At High Pressure. To Check Whether My Rules Were Just My Imagination Or the Were True I Predicted New Structures of Similar Compounds. For example LIBR OR NABE and Some Combinations Like This. And Yes, These Rules Turn Out to Be Followed. In Short, Just Not to Be Very Specialistic, I'Ve Seen That There Is A Tendency: When You Compress Them The Would Form Two-Dimensional Metals, Then One-Dimensional Structure of Metal. And Then at Very High Pressure Some More Wild Would Happen Because The Cl in This Case Will Have the Oxidation Number of -2. All The Lowest Oxidation Number of Cl IS -1, Which Is Typical Textbook Example: Sodium Loses It. SO WE HAVE +1 AND -1 OXIDATION NUMBERS. But At a Very High Pressure It Is Not True Anymore. We demonstrated this with some approaches for chemical bonding analysis. In That Work Also I TriD to Look At The Literature to See If Somebody Have Seen This Kind of Rules Before. And yes, it TURNED OUT THAT THERE WERE SOME. If I'm Not Mistaken, Na-Bi and Other Compounds Turned Out to Follow These Rules. IT IS JUST A Starting Point, of Course. The Other Papers Will Come Up and We Will See Whether This Model Has A Real Predictive Power. Because This Is What We Are Looking For. We Wa Want to Sketch The Chemistry Which Will Work Also for High Pressure.
Figure 12. The structure of the substance with the chemical formula Na 4 Cl 3, which is formed at a pressure of 125-170 GPaIt clearly demonstrates the appearance of a "strange" chemistry under pressure.
Despite the fact that the USPEX algorithm is characterized by a large predictive force within its tasks, the theory always requires experimental verification. The laboratory of computer design materials is the theoretical, as follows from its name. Therefore, experiments are held in collaboration with other scientific groups. The study strategy adopted in the laboratory, Gabriel Saleh comments as follows:
"We do not conduct experiments - we are theorists. But often we cooperate with people who do it. In fact, I think it is generally difficult. Today, science is narrowly specialized, so it's not easy to find someone who is engaged in both the other " .
WE DON'T Do Experiments, But Often We Collaborate with Some People Who Do Experiments. Actually i Think in Fact It's Hard. Nowadays The Science Is Very Specialized So It's Hard to Find Somebody WHO Does Both.
One of the brightest examples is a prediction of transparent sodium. In 2009 in the journal Nature. The results of work performed under the guidance of Artem Oganova were published. In the article, scientists described the new form of Na, in which it is transparent nonmetal, becoming a dielectric pressure. Why is this happening? This is due to the behavior of valence electrons: under pressure, they are displaced in the voids of the crystal lattice formed by sodium atoms (Fig. 13). At the same time, the metal properties of the substance disappear and the qualities of the dielectric appear. The pressure of 2 million atmospheres makes sodium red, and 3 million - colorless.
Figure 13. Sodium under pressure is more than 3 million atmospheres. Blue blossom The crystal structure from sodium atoms is shown, orange - bunches of valence electrons in the voids of the structure.
Few people believed that the classic metal could demonstrate such behavior. However, in collaboration with physician Mikhail Eremez, experimental data were obtained that fully confirmed the prediction (Fig. 14).
Figure 14. Photos of the Na sample obtained by combining passing and reflected lighting. Different pressure was applied to the sample: 199 GPa (transparent phase), 156 GPa, 124 GPa and 120 GPa.
Artem Yoganov told us what claims he places to his employees:
"First, they must have a good education. Secondly, being workers. If the man is lazy, then I will not take it to work, and if suddenly I will take it, he will be abused. Several employees who were lazy, inert, amorphous, I just fired. And I think it is absolutely correct and good even for the person himself. Because if a person is not in his place, he will not be happy. He needs to go there, where he will work with a light, with an enthusiasts, with pleasure. And this is good for the laboratory, and good for a person. And those guys who really work beautifully, with a twinkle, the fact that we pay a good salary, they go to the conference, they write articles that then go to the best magazines, they will be fine. Because they are in their place and because the laboratory has good resources in order to support them. That is, the guys do not need to think about the acquisition to survive. They can concentrate on science, on their favorite business, and successfully deal with them. We have now appeared some new grants, and it opens up the opportunity to hire a few more people. Competition is constantly. All year round people submit applications, I take, of course, not all. ". (2016). 4-aminopyridine crystallide, a method of obtaining, a pharmaceutical composition and a method of treatment and / or prevention on its basis. Phys. Chem. Chem. Phys. 18 , 2840–2849;
We publish the text of the lecture read by Professor at the University of New York, Adjunct Professor MSU, honorary professor of the Guilign University Artem Ohanov 8 September 2012 in the framework of the cycle of "Public Lectures" Polit.ru "at the open-air book festivalBookmarket. In the art park "Museon".
"Polyant.ru public lectures" are held with the support:
I am very grateful to the organizers of this festival and "Polit.ru" for the invitation. It is a great honor for me to read this lecture; I hope she will be interesting to you.
The lecture is directly related to our future, because our future is impossible without new technologies, technologies relating to our quality of life, here is the iPad, here is our projector, all our electronics, energy-saving technologies, technologies that are used to clean the environment, technologies that It is used in medicine and so on - all this depends to a vastity of new materials, new technologies require new materials, materials with unique, special properties. And how these new materials can be developed not in the laboratory, but on the computer, will go a story.
The lecture is called: "Computer design of new materials: a dream or reality?". If it was a very dream, the lecture would not make sense. Dreams are something, as a rule, not from the reality area. On the other hand, if it was already fully implemented, the lecture would also have no sense, because the new kind of methodology, including theoretical computing, when they are already fully developed, are moving from the discharge of science in the category of industrial routine problems. In fact, this area is completely new: the computer design of new materials is somewhere contemporated between the dream - the fact that it is impossible, what we dream of leisure - and reality, it is not until the end of the completed area, which is an area that Developed right now. And this area will allow in the near future to retreat from the traditional method of opening new materials, laboratory, and proceed to computer design materials, it would be cheaper, and faster, in many ways, even more reliable. But how to do it, I will tell. This is directly related to the problem of prediction, the forecast of the structure of the substance, because the structure of the substance determines its properties. The various structure of the same substance, say, carbon, determines the superterald diamond and super might-dimensional graphite. The structure in this case is all. Structure of substance.
In general, we celebrate the centenary of the first experiments this year, which allowed to open the structure of the substance. Very long ago, with ancient times, people put forward hypothesis that the substance consists of atoms. The mention of this can be found, for example, in the Bible, in various Indian epic, and quite detailed references to this can be seen from Democrita and the Lucreta Kara. And the first mention of how the substance is arranged, as this substance consists of these discrete particles, atoms, belong to Johann Kepleru, a great mathematics, astronomer and even an astrologer - at that time astrology was considered a science, unfortunately. Kepler drew the first pictures in which he explained the hexagonal shape of snowflakes, and the ice structure proposed by Kepler, although it differs from reality, in many aspects it is similar. But, nevertheless, the hypothesis about the atomic structure of the substance remained a hypothesis until the 20th century, until a hundred years ago, for the first time, this hypothesis was not scientifically proven. She became proven with my science, crystallography, science relatively new, which was born in the middle of the 17th century, 1669 is the official date of birth of crystallography science, and created her wonderful Danish scientist Nikolai Wyton. In fact, his name was Niels Szensen, he was a Dane, a latinized name - Nikolai Wallon. He founded not only crystallography, but a number of scientific disciplines, and it formulated the first law of crystallography. From this time, the crystallography at a farewell trajectory began its development.
Nikolai Stenon had a unique biography. He became not only the founder of several sciences, but also ranked the face of the Saints Catholic Church. The crystallograph was also the greatest German poet Goethe. And Goethe belongs to the quotation that crystallography is unproductive, exists inside itself, and in general, this science is completely useless, and it is not clear why it is needed, but as a puzzle is very interesting, and due to this attracts very smart people. So spoke Goethe in a popular skip lecture, which he read somewhere on the Baden resorts rich in idle ladies. By the way, there is a mineral called in honor of Goethe, goes away. It must be said that at that time the crystallography was indeed quite useless science, really at the level of some mathematical Sharad and Puzzles. But time passed, and 100 years ago, crystallography came out from the category of such science in himself and became science extremely useful. This was preceded by a big tragedy.
I repeat, the atomic structure of the substance remained a hypothesis until 1912. The Great Austrian Physicist Ludwig Boltzman built all his scientific arguments on this hypothesis about the atomicity of the substance and was severely criticized by many of his opponents: "How can you build all your theories on an unproved hypothesis?" Ludwig Boltzman under the influence of this criticism, as well as weak health, committed itself in 1906. He hanged himself, being on vacation with his family in Italy. Only 6 years later, the atomic structure of the substance was proven. So if he was a little more patient, he would have tried over all his opponents. Patience sometimes means more than the mind, patience means more than even genius. So - what were these experiments? These experiments were made by Max von Laue, more precisely, his graduate students. Max von Laue himself did not make any such experiments, but the idea belonged to him. The idea was that if the substance really consists of atoms, unless, as Kepler assumed, atoms were built in a crystal periodic in a regular way, then an elevated phenomenon should be observed. Shortly before the X-rays were discovered. Physics by that time were already well understood that if the radiation wavelength is comparable with a length of periodicity - a characteristic length of the object, in this case - a crystal, then the diffraction phenomenon should be observed. That is, the rays will travel not only strictly in a straight line, but also to deviate on completely strictly certain angles. Thus, the crystal should be observed some completely special picture of X-ray diffraction. It was known that the wavelength of X-ray radiation should be similar to the size of atoms, if atoms exist, estimates of the size of atoms were made. Thus, if the atomic hypothesis of the structure of the substance is correct, the diffraction of X-rays of crystals should be observed. What could be easier to check?
A simple idea, a simple experiment, for which a little more than in a year, Laue Got a Nobel Prize in Physics. And we can try to spend this experiment. But, unfortunately, now too light, so that this experiment can observe everything. But maybe we will try this with one witness? Who could come here and try to observe this experiment?
See. Here is a laser pointer, we will shine to her - and what happens here? We do not have X-rays, but an optical laser. And this is not the structure of the crystal, and its image bloated by 10 thousand times: But after all, the laser wavelength is 10 thousand times higher than the wavelength of the X-ray radiation, and thus the diffraction condition is again made - comparability of the wavelength with a period of crystal lattice. Here we look at the object in which there is no regular structure, liquid. Here, Oleg, hold this picture, and I will shine a laser, come closer, the picture will be small, because we cannot project ... Look, you see the ring here, inside - a point that characterizes the direct passage of the beam. But the ring is the diffraction from the inorganized fluid structure. If the crystal is before us, then the picture will be completely different. You see, we have a lot of rays that deflect on strictly certain angles.
Oleg (volunteer):Probably because more atoms ...
Artyom Yoganov: No, due to the fact that atoms are located strictly in a certain way, we can observe such a picture of the diffraction. This picture is very symmetrical, and it is important. Let's find Oleg for a brilliantly conducted experiment, which would bring the Nobel Prize 100 years ago.
Next - the next year, the father and son of Bragg learned to decipher the diffraction pictures, determine the crystal structures. The first structures were very simple, but now thanks to the latest methodologies for which the Nobel Prize was awarded in 1985, it is already possible to decipher already very, very complex structures based on the experiment. Here is the experiment that I and Oleg reproduced. Here is the source structure, there is a benzene molecule, and the Oleg observed such a diffraction picture. Now, with the help of the experiment, it is possible to decipher very complex structures, in particular the structure of quasicrystals, and for the opening of quasicrystals, this new state of the solid substance, last year the Nobel chemistry premium was given. How dynamic is this area, what fundamental discoveries are performed on our century! The structure of proteins and other biologically active molecules is also decoded by the X-ray learning diffraction, this great crystallographic method.
So, we know the various states of the substance: ordered crystalline and quasicrystalline, amorphous (disordered solid state), as well as liquid, gaseous condition and various polymer states of the substance. Knowing the structure of the substance, you can predict many and many of its properties, and with a great degree of reliability. Here is the structure of magnesium silicate, type perovskite. Knowing the approximate positions of atoms, you can predict, for example, such a rather difficult property, as elastic constant - this property is described by a rank tensor with a multitude of component, and this complex property you can predict with experimental accuracy, knowing only the position of atoms. And the substance is quite important, it is 40% of the volume of our planet. This is the most common material on Earth. And now to understand the properties of this substance that exists at high depths, it is possible, knowing only the location of atoms.
I would like to tell a little about how property properties are associated as predicting the structure of the substance so that new materials can be predicted, and what has been done with this kind of methods. Why is ice lighter than water? We all know that icebergs are swimming and not drown, we know that ice is always on the surface of the river, and not at the bottom. What's the matter? The case is in the structure: if you look at this structure of ice, then you will see large hexagonal empties in it, and when the ice begins to melt, the water molecules clog these hexagonal emptiness, due to this water density becomes greater than the density of the ice. And we can demonstrate how this process is happening. I will show you a short film, look carefully. Melting will begin with surfaces, so it really happens, but this is a computer calculation. And you will see how melting spreads inside ... Molecules are moving, and you see how these hexagonal channels are clogged, and the correctness of the structure is lost.
The ice has several different forms, and a very interesting form of ice, which turns out if you score the emptiness of the ice structure by guest molecules. But the structure itself will also change. I am talking about the so-called gas hydrates or clathrates. You see the frame of water molecules in which there are voids in which guest molecules or atoms are present. Guest molecules may be methane - natural gas, can be carbon dioxide, maybe, for example, an atom of xenon, and each of these gas hydrates has an interesting story. The fact is that methane hydrate reserves contain 2 orders of magnitude more than natural gas than traditional gas fields. The deposits of this type are located, as a rule, on the sea shelf and in the zones of permafrost. The problem is that people have not yet learned to safely and profitably extract gas from them. If this problem is solved, humanity will be able to forget about the energy crisis, we will have a practically an inexhaustible source of energy for the coming centuries. Hydrogen carbon dioxide is very interesting - it can be used as a safe method of disposal of excess carbon dioxide. You download carbon dioxide under low pressure in the ice and throw it on the seabed. This ice there is completely calmly there are many thousands of years. Xenon's hydrate served as an explanation of xenon anesthesia, a hypothesis, which 60 years ago was nominated by the Grand Crystalochemist Linus Polingom: The fact is that if a person is given to raise xenon under low pressure, a person ceases to feel pain. It was used and, it seems, is now sometimes used for anesthesia in surgical operations. Why?
Xenon under low pressure forms compounds with water molecules, forming the same gas hydrates, which clog the spread of the electrical signal over the human nervous system. And the pain signal from the operated fabric simply does not reach the muscles, due to the fact that it is precisely with such a structure, xenon hydrate. It was the very first hypothesis, perhaps the truth is more complicated, but there is no doubt that the truth is near. When we talk about such porous substances, it is impossible not to recall microporous silicates, the so-called zeolites, which are very widely used in industry for catalysis, as well as for separating molecules with oil cracking. For example, octane and mesoochean molecules are perfectly separated by zeolites: this is the same chemical formula, but the structure of molecules is a little different: one of them is long and thin, the second is short and thick. And the one who is thin, passes through the voids of the structure, and the one that is thick, is sifted, and therefore such structures, such substances are called molecular sieves. These molecular sieves are used to purify water, in particular, the water that we drink, in our cranes, it should pass through multiple filters, including with the help of zeolites. You can thus get rid of contamination with the most different chemical pollutants. Chemical pollutants are sometimes extremely dangerous. The story knows examples of the poisoning of heavy metals led to very sad historical examples.
Judging throughout the victims of mercury poisoning were the first first emperor of China - Qin Shihuandi, and Ivan the Terrible, and the so-called crazy hat was studied very well, in 18-19 centuries in England a whole class of people working in the hat industry was very early The neurological disease called the disease of the crazy hat. Their speech became incoherent, their actions are meaningless, their limbs were uncontrolled trembled, and they fell in dementia and madness. Their body was constantly in contact with mercury, as they soaked these hats in solutions of mercury salts, which fell into their body and hit the nervous system. Ivan Grozny was very progressive, a good king at the age of 30, after that he had changed overnight - and became an insane tyrant. When his body was exhumed, it turned out that he had sharply deformed bones, and they contained a huge concentration of mercury. The fact is that the king suffered from a serious form of arthritis, and at that time arthritis was treated with rubbing mercury ointments - it was the only remedy, and perhaps just mercury explains the strange madness of Ivan the Terrible. Qin Shihuandi, a person who created China in his current form, rules of 36 years old, and the first 12 years he was a puppet in his mother's hands, rents, his story is similar to History of Hamlet. Mother and her lover killed his father, and then tried to get rid of himself and the story is terrible. But, it was imperative, he began to rule himself - and for 12 years he stopped the civil war between the 7 kingdoms of China, which lasted 400 years, united China, he combined the weight of weight, money, unified Chinese writing, he built a great Chinese wall, he built 6 , 5 thousand kilometers of highways, which are still used, channels that are still used, and this has done one person, but in recent years he suffered some strange form of manic madness. His alchemists in order to make him immortal gave him mercury pills, they believed that it would make him immortal, as a result, this person, apparently, distinguished by random health, died, not lived and up to 50 years, and the last years of this short life were Omrocheted madness. Lead poisoning, possibly made by his victims of many Roman emperors: In Rome there was a lead water pipe, aqueduct, and it is known that with lead poisoning, certain brain departments are cut, it is possible to see it even on tomographic pictures, the intelligence falls, IQ falls, the person becomes very aggressive . Lead poisoning - to this day a big trouble of many cities and countries. To get rid of this kind of undesirable consequences, we need to develop new materials for cleaning the environment.
Interesting materials, not fully explained, are superconductors. Superconductivity was also open 100 years ago. This phenomenon is largely exotic, it was openly open. Just cooled mercury in liquid helium, the electrical resistance was measured, it turned out that it drops smoothly to zero, and later it turned out that superconductors completely push the magnetic field and are able to levitate in a magnetic field. These two characteristics of superconductors are used quite widely in high-tech applications. The type of superconductivity, which was opened 100 years ago, was explained, the explanation was required by half a century, this explanation brought the Nobel Prize John Bardin and his colleagues. But then in the 1980s, already on our century, a new type of superconductivity was opened, and the best superconductors belong to this class - high-temperature superconductors based on copper. An interesting feature is that such superconductivity still has no explanation. Applications from superconductors a lot. For example, using superconductors create the most powerful magnetic fields, and this is used in magnetic resonance imaging. Levishing trains on magnetic rolling - Another application, and here is a photo that I personally did in Shanghai on such a train - a speed indicator of 431 kilometers per hour is visible. Superconductors are sometimes very exotic: Already 30. Organic superconductors are known to 30 years old, i.e. carbon-based superconductors, it turns out, even a diamond can be made, entering it a small amount of boron atoms. Graphite can also be made superconductor.
Here is an interesting historical parallel about how the properties of materials or their ignorance can have fatal consequences. Two stories that are very beautiful, but, apparently, are historically wrong, but I will still tell them, because a beautiful story is sometimes better than the truthful story. In popular science literature, it is very often possible to meet references to how the effect of tin plague - and its sample - destroyed the expedition of Napoleon in Russia and Captain Scott to the southern pole. The fact is that a tin at a temperature of 13 degrees Celsius undergoes a transition from metal (this is white tin) into a gray tin, a semiconductor, while the density drops sharply - and the tin falls apart. This is called "tin plague" - tin simply is crumpled. And here is the story that I have not met a full explanation. Napoleon comes to Russia with a 620 thousandth army, gives only a few relatively small battles - and it comes to Borodin only 150 thousand people. 620 comes to Borodin almost without a combat comes 150 thousand. With Borodina, about 40 thousand victims, then a retreat from Moscow - and 5 thousand people reach Paris. By the way, and the retreat was also almost without a fight. What is going on? How from 620 thousand without a fight to ride up to 5 thousand? There are historians who claim to be to blame for all tin plague: the buttons on the uniforms soldiers were made of tin, the tin crumbled, as soon as the cold came, - and the soldiers turned out to be actually naked in Russian frost. The problem is that the buttons were made of a dirty tin, which is steadily for tin plague.
Very often, you can see in a popular science press mention that Captain Scott in different versions either with himself airplanes in which the fuel tanks had tin solders, or canned food in tin banks again crumbled, and the expedition died from hunger and cold. I actually read the diaries of Captain Scott - he did not mention any airplanes, he had some Aerosani, but again he does not write about the fuel tank, and he also does not write about canned food. So these hypotheses, apparently, are incorrect, but very interesting and instructive. And remember the effect of tin plague in any case is useful if you are going to the cold climate.
Here is another experience, and then I will need boiling water. Another effect associated with materials and their structure, which would not have come to one person, - the effect of the forms, also open quite by chance. In this illustration, you see that my colleagues made two letters from this wire: T U, Technical University, they have hardered this form at high temperatures. If you order some form at high temperatures, the material will remember this form. You can make a heart, for example, to give a sweetheart and say: this heart will remember my feelings forever ... Then this form can be destroyed, but as soon as you give it into hot water, the form is restored, it looks like magic. You have just broke this form, but put into hot water - the form is restored. And all this is due to a very interesting and fairly thin structural transformation, which occurs in this material at a temperature of 60 degrees Celsius, which is why they need hot water in our experience. And the same transformation occurs both in steel, but in steel it occurs too slowly - and the memory of the form effect does not occur. Imagine if the steel also showed such an effect, we would live in a completely different world. The effect of the form of the form finds a lot of applications: dental brackets, cardiac shunts, parts of the engine in airplanes to reduce noise, spikes in gas pipelines and oil pipelines. And now I need another volunteer ... Please what is your name? Vika? We will need Help Wiki with this wire, this is a wire memory wire. The same alloy Nitinol, alloy of nickel and titanium. This wire was tempered in the form of a straight wire, and it will remember this form forever. Vika, take a piece of this wire and his every way to crowding, make it so that it is indirect as possible, only nodes do not tie: the node does not raise. And now they are poking him in boiling water, and the wire will remember this form ... Well, how, straightened? This effect can be observed forever, I probably saw him a thousand times, but every time, as a child, I look and admire what a beautiful effect. Let's climb a Vika. It would be nice if we learned such materials to predict on the computer.
But the optical properties of materials that are also completely nontrivial. It turns out, many materials, almost all the crystals, split the beam of light on two beams, which travel in different directions and at different speeds. As a result, if you look through a crystal on some inscription, then the inscription will always be a little bit. But, as a rule, indistinguishable for our eye. In the Sore crystals, this effect is so strong that you can really see two inscriptions.
Question from the hall:Did you say - at different speeds?
Artem Oganov:Yes, the speed of light is constant only in vacuum. In condensed media, it is lower. Next, we are accustomed to think that each material has a defined color. Ruby - red, sapphire - blue, but it turns out, the color also may depend on the direction. In general, one of the main characteristics of the crystal is anisotropy - the dependence of property properties. Properties in this direction and in this direction vary. Here is the mineral Cordieritis, which in different directions the color changes from brownish-yellow to blue, this is the same crystal. Does anyone believe me? I brought a special Cordierite crystal to, please ... look what color?
Question from the hall:It seems white, but so ...
Artem Oganov:From some light, like white, to violet, you just rotate the crystal. In fact, there is an Icelandic legend on how Vikings opened America. And many historians see in this legend an indication of using this effect. When the Vikings were lost in the midst of the Atlantic Ocean, their konung took out a certain solar stone, and in the twilight light managed to determine the direction to the West, and so they walked to America. What is solar stone, no one knows, but many historians believe that the sunny stone is that Vika keeps in his hands, Cordieritis, by the way, Cordierit is found off the coast of Norway, and with the help of this crystal can really navigate in the twilight light in Evening light, as well as in polar latitudes. And this effect was used by the US Air Force up to the 50s, when more advanced ways came to replace it. But another interesting effect - Alexandrite, if anyone has a desire, I brought the crystal synthetic alexandrite, and its color changes depending on the light source: in day and electric. And finally, another interesting effect, which many centuries could not understand scientists and art historians. The Likurg's Bowl is an object that was made by Roman craftsmen more than 2 thousand years ago. In the scattered light, this bowl has a green color, and in the passing - red. And it was possible to take it literally a few years ago. It turned out that the bowl was not made of pure glass, but contains gold nanoparticles, which create this effect. Now we understand the nature of the color - the color is associated with certain absorption ranges, with an electronic structure of the substance, and this, in turn, is connected with the atomic structure of the substance.
Question from the hall:The concepts "reflected" and "passing" can be explained?
Artem Oganov:Can! By the way, I note that these very absorption spectra are determined why Cordieritis is different color in different directions. The fact is that the structure itself is a crystal - in particular, Cordieritis - looks different in different directions, and light in these directions is absorbed in different ways.
What is white light? This is the whole spectrum from red to violet, and when the light passes through the crystal, part of this range is absorbed. For example, a crystal can absorb blue, and what will happen as a result, you can see from this table. If you absorb the blue rays, then at the output you will have an orange color, that is, when you see something orange, you know that this substance absorbs in the blue range. The scattered light is when you have the same Licharge bowl on the table, the light falls, and some of this light dissipates and falls into your eyes. Light scattering obeys completely different laws and, in particular, depends on the grain of the object. Thanks to the scattering of light blue sky. There is a law of Rayleigh scattering, with which you can explain these colors.
I demonstrated you how properties are associated with the structure. And how can I predict the crystal structure, we will look briefly now. So, the task of predicting crystal structures until recently was considered unresolved. This task itself is formulated as follows: how to find the location of atoms, which gives maximum stability - that is, the lowest energy? How to do it? You can, of course, go through all the options for the location of atoms in space, but it turns out that such options are so much that you don't have enough life to go through, in fact, even for fairly simple systems, let's say, with 20 atoms, you will need more than time Life of the Universe to go through all these possible combinations on the computer. Therefore, it was believed that this task is unreserved. Nevertheless, this task was solved, and several methods, and the most effective method, although it may be immodally sounded, was developed by my group. The method is called "success", "uspex", an evolutionary method, an evolutionary algorithm, the essence of which I will try to explain to you now. The task is equivalent to finding a global maximum on a multidimensional surface - for simplicity, consider a two-dimensional surface, the surface of the earth, where you need to find the highest mountain, without having cards. Let's formulate it as it formulated this is my Australian colleague Richard Clegg - he is a Australian, he loves Kangaroo, and in its wording with a kangaroo, sufficiently non-intellectual animals, you need to determine the highest point on the ground surface. Kangaroo understands only simple instructions - go up, go down. In the evolutionary algorithm, we throw off the landing Kangaroo, by chance, in different points of the planet and give each of them the instructions: Go up, to the top of the nearest hill. And they go. When these kangaroo reach the sparrow mountains, for example, and when it comes to Elbrus, and those who have not got high, are shifted, shoot. The hunter comes, almost said the artist, the hunter comes and shoots, and those who survived, get the right to multiply. And thanks to this, it is possible to single out the most promising areas of the search space. And step by step, shooting more and higher kangaroo, you shift the kangaroo population to the global maximum. The kangaroo will produce more and more successful offspring, hunters will shoot more and more highly climbing kangaroo, and thus you can simply drive this population.
And this is the essence of evolutionary methods. For simplicity, I lower the technical details, as it was precisely implemented. And here is another two-dimensional implementation of this method, there is an energy surface, we need to find the very blue point, our original, random, structures are these fat points. The calculation immediately understands which of them are bad, here in the red and yellow areas, which of them are the most promising: in blue, greenish fields. And step by step the density of testing the most promising areas is growing until we find the most adapted, most stable structure. There are different methods for predicting structures - methods of accidental search, artificial annealing, and so on, but the most powerful method was this, evolutionary.
The most difficult thing is how to produce descendants from the parents on the computer. How to take two parent structures and make a child of them? In fact, you can make children not only from two parents on the computer, we experimented, we tried from three and from four to do. But, as it turns out, it does not lead to anything good, just like in life. The child is better if two parents. One parent, too, by the way, works, two parents are optimal, and three or four are no longer working. The evolutionary method has several interesting features that, by the way, are relative to this with biological evolution. We see how from unsuitable, random structures from which we begin the calculation, highly organized, highly ordered solutions appear during the calculation. We see that the calculations are most effective when the population of the structures is the most diverse. The most stable and most surviving populations are a diversity population. For example, what I like Russia is the fact that in Russia - 150 with more than nations. There are blonde, there are dark-haired, there are all sorts of Caucasian nationality faces like me, and all this gives the Russian population stability and future. Monotonous populations of the future do not have. This can be seen from the epolutions calculations extremely clear.
Can we predict that the stable form of carbon at atmospheric pressures is graphite? Yes. This calculation is very fast. But in addition to graphite, we produce a few interesting slightly less stable solutions in the same calculation. And these decisions can also be interesting. If we raise the pressure - graphite is already unstable. And the stable diamond, and we also find it very easily. See how from disordered initial structures, the calculation quickly produces diamond. But before the diamond is found, a number of interesting structures are produced. For example, this structure is. While the diamond has hexagonal rings, 5 and 7 coal rings are visible. This structure is only slightly inferior in stability diamond, and at first we thought it was curious, and then it turned out that this is a new, real-life carbon form that was installed quite recently by us and our colleagues. This calculation was made at 1 million atmospheres. If we press up to 20 million atmospheres, the diamond will cease to be stable. And instead of the diamond, a very strange structure will be stable, about the stability of which for carbon at such pressures has already guessed many decades, and our calculation confirms it.
A lot of what was done both by us, and our colleagues with this method, in front of you a small selection of different discoveries. Let me only tell me about some of them.
With this method, you can replace the laboratory opening of materials on a computer. In the laboratory opening of materials, the unsurpassed champion was Edison, who said: "I did not suffer 10 thousand failures, I only found 10 thousand ways that do not work." It tells you about how much attempts need, unsuccessful attempts to commit before performing a real discovery by this method, and with the help of computer design you can seek success in 1 attempt out of 1, 100 out of 100, 10 thousand out of 10 thousand, this is our The goal is to replace the Edison method on something much more productive.
We can now optimize not only energy, but also any property. The simplest property is the density, and the most dense material from the well-known diamond is still. Almaz generally record holder in many ways. The diamond cubic centimeter contains more atoms than in a cubic centimeter of any other substance. Almaz - hardware record holder, and this is also the least compressible substance from those known. Is it possible to beat these records? Now we can ask this question to the computer, and the computer will answer. And the answer is yes, you can beat some of these records. It turned out that on the density of diamond to beat quite easily, there are more dense forms of carbon, which are eligible for existence, but not yet synthesized. These carbon forms beat a diamond not only by density, but also by optical properties. They will have higher refractive indices and dispersion of light - what does this mean? The refractive index of the diamond provides a diamond to its unsurpassed shine and an internal reflection of light - and the dispersion of light means that the white light will split on the spectrum from red to violet even more than the diamond makes it. Here, by the way, the material that often replaces the diamond in the jewelry industry is cubic zirconium dioxide, fianit. It exceeds the diamond on the dispersion of light, but, unfortunately, is inferior to a glitter diamond. And new carbon forms will win a diamond on both indicators. What about hardness? Until 2003, it was believed that hardness is a property that people will never learn to predict and expect, in 2003 everything has changed with the work of Chinese scientists, and this summer I visited the Yankan University in China, where I received another degree of honorary professor, and there I visited the founder of all this theory. This theory we managed to develop.
Here is a table that shows how the estimated definitions of hardness are consistent with the experiment. For most normal substances, the consent is excellent, but for graphite the model predicted that it should be super humus, which is obviously incorrect. We managed to understand and eliminate this error. And now, with the help of this model, we reliably predict hardness for any substances, and we can set the following question to the computer: what substance is the hardest? Is it possible to exceed the diamond of hardness? People actually thought about it many a few decades. So, what is the firm structure of carbon? The answer was discouraging: diamond, and there can be nothing more solid in carbon. But you can find carbon structures that will be close to diamond. Carbon structures that are close to diamond hardness, really have the right to exist. And one of them is the one I showed you before, with 5- and 7-membered channels. Dubrovinsky in 2001 was proposed in the literature the ultraceal substance - titanium dioxide, it was believed that he was doubtfully inferior to the diamond, but there were doubts. The experiment was quite controversial. Almost all experimental measurements from that work were sooner or later refuted: the hardness to take was very difficult, due to the small size of the samples. But the calculation showed that the hardness was also erroneously measured in the experiment, and the real hardness of titanium dioxide is about 3 times less than the experimenters asserted. So with this kind of calculations, you can even judge what experiment is reliable, which is not, so these calculations have now reached high accuracy.
Another story that I would like to tell you is connected with carbon - it is especially rapidly unfolding in the last 6 years. But she began 50 years ago, when such an experiment was conducted by American researchers: they took graphite and squeezed it to a pressure of about 150-200 thousand atmospheres. If graphite is compressed at high temperatures, it must go into the diamond, the most stable carbon shape at high pressures is precisely so diamond and synthesize. If you do this experiment at room temperature, then the diamond cannot form. Why? Because the restructuring of the structure that is required to transform graphite in diamond, the solids are large, too unlike these structures, and the energy barrier to be too large to overcome. And instead of the formation of diamond, we will observe the formation of a certain other structure, not the most stable, but the one that the least high barrier of education. We offered such a structure - and called it M-carbon, this is the most structure with 5- and 7-membered rings; My Armenian friends jokingly call him "Mugleod-Schmugarod". It turned out that this structure fully describes the results of the experience of 50 years ago, and the experience was repeated many times. Experience, by the way, is very beautiful - squeezing at room temperature graphite (black, soft opaque semimetal), under pressure, researchers received a transparent super-high non-metal: completely fantastic transformation! But this is not a diamond, its properties are not consistent with the diamond, and our hypothetical then the structure fully described the properties of this substance. We were terribly delighted, wrote an article and published it in the prestigious Journal of Physical Review Letters, and worshed the smooth year on the laurels. A year later, American and Japanese scientists found a new structure, completely different from her, this, with 4- and 8-membered rings. This structure is completely different from our, but almost as well describes experimental data. The problem is that the experimental data was low permission, and many other structures were suitable for them. For another six months, the Chinese invited W-carbon on the name, and W-carbon also explained the experimental data. Soon the story became a grotesque - new Chinese groups joined it, and the Chinese love to produce, and they found about 40 structures, and they are all suitable for experimental data: P-, Q-, R-, S-carbon, Q-carbon, x -, Y-, Z-carbon, M10-carbon is known, X'-carbon, and so on - already the alphabet is not enough. So who is right? In general, speaking, the rights of claims on the rightness of our M-carbon at first were exactly the same as many others.
Replica from the hall:All right.
Artem Oganov:This also does not happen! The fact is that nature always chooses extreme solutions. Not only people extremists, but also nature is also an extremist. At high temperatures, nature chooses the most stable state, because at high temperatures you can go through any energy barrier, and at low temperatures, nature chooses the smallest barrier, and only one can be the winner here. The champion can be only one - but who exactly? It is possible to conduct a high resolution experiment, but people tried 50 years old, and no one succeeds, all the results were low quality. You can carry out the calculation. And in the calculation it would be possible to consider the activation barriers to the formation of all these 40 structures. But, first, the Chinese still stamps new and new structures, and no matter how much you tried, any equal to any Chinese, who will say: And I have another structure, and you will take these until the end of life. Activation barriers until you are sent to a well-deserved rest. This is the first complexity. The second difficulty is to consider the activation barriers very and very hard in solid transformations, this is a task that is extremely nontrivial, you need special methods and powerful computers. The fact is that these transformations occur not in the whole crystal, but at the beginning in a small fragment - an embryo, and then it spreads to the germ further. And model this germ is an extremely difficult task. But we found this method, the method that was developed before the Austrian and American scientists, and adapted it to our task. We managed to modify this method so that we could solve this task once and for all. We set the task as follows: if you start with graphite, a rigidly specified initial state, and the final state is specified vague - any tetrahedral, SP3-hybridized carbon form (namely, we expect under pressure), then which barriers will be minimal? This method knows how to count the barriers and finds a minimum barrier, but if we specify the final condition as an ensemble of different structures - then we can solve the problem completely. We started the calculation of the transformation of graphite - diamond as a "seed", we know that this transformation is not observed in the experiment, but we were interested - what makes the calculation with this transformation. We waited a little (in fact, this calculation took six months on a supercomputer) - and the calculation instead of the diamond was issued by m-carbon.
In general, I must say, I have an extremely lucky person, I had a chance to win 1/40, because there were about 40 structures that had an equal chance to win, but a lottery ticket again I pulled out. Our M-carbon won, we have published our results in the prestigious new Journal Scientific Reports - this is a new Nature group magazine, and a month after we have published our theoretical results, the results of the high resolution experiment, for the first time in 50 years obtained. Researchers from Yale University made a high resolution experiment and checked all these structures, and it turned out that only M-carbon satisfies all experimental data. And now in the list of carbon forms there is another experimentally and theoretically installed carbon altropy, m-carbon.
I mention about another alchemical transformation. Under pressure it is expected that all substances will turn into a metal, sooner or later, any substance will become metal. And what will happen to the substance that is initially already metal? For example, sodium. Sodium is not just a metal at all, but an amazing metal describing the model of free electrons, that is, this is the maximum case of a good metal. What will happen if to surrender sodium? It turns out that sodium will cease to be a good metal - at the beginning of the sodium will turn into a one-dimensional metal, that is, electricity will be carried out in only one direction. At a higher pressure, we predicted that sodium will lose metal in general and turn into a reddish transparent dielectric, and if the pressure is even greater, it will become colorless, like a glazy. So - you take a silver metal, squeeze it - first it turns into a bad metal, black, like coal, comprehend more - it turns into a reddish transparent crystal, outwardly resembling Ruby, and then it becomes white, like Steklyushko. We predicted it, and the Nature magazine, where we sent it, refused to publish it. The editor has returned the text for several days and said: We do not believe, too exotic. We found an experimenter, Mikhail Eramtsz, who was ready to check this prediction - and that's the result. With a pressure of 110 gigapascular, it is 1.1 million atmospheres, it's still silver metal, at 1.5 million atmospheres - it is black as coal bad metal. With 2 million atmospheres - this is a transparent reddish nonmetall. And already with this experiment, we very easily published our results. This is, by the way, a fairly exotic state of the substance, because electrons are no longer smeared in space (both in metals) and are not localized on atoms or on ties (as in ionic and covalent agents) - valence electrons that sodium provided metal, clamped in voids Spaces where there are no atoms, and they are very much localized. Such a substance can be called an electride, i.e. Salt, where the role of negatively charged ions, anions, do not perform atoms (say, fluorine, chlorine, oxygen), and bunches of electron density, and our sodium form is the easiest and most vivid example of an electride from well-known.
You can use this kind of calculations and for understanding the substance of the earth and planetary subsoil. We learn about the state of earthly subsoils mainly on indirect data, according to seismological data. We know that there is a metallic, mainly consisting of iron, the core of the Earth, and the non-metallic, consisting of magnesium silicates, a shell, called mantle, and at the surface itself - the thin crust on which we live, and which we know just very OK. And the insides of the earth are unknown to us almost at all. Direct testing we can only explore the most surface of the earth. The deepest well is Kola ultrawow, its depth is 12.3 kilometers, drilled in the USSR, no one could get better. The Americans tried to climb, broke on this project and stopped it. In the USSR, there were huge amounts, Dober up to 12 kilometers, then the restructuring happened, and the project was frozen. But the radius of the Earth is 500 times more, and even the Kola ultra-deep well drilled only the surface of the planet. But the substance of the depths of the Earth defines the Lac of Earth: earthquake, volcanism, continent drift. The magnetic field is formed in the Earth's kernel, which we never get to us. Convection of the molten external core of the Earth and is responsible for the formation of the Earth's magnetic field. By the way, the inner core of the Earth is solid, and the external - melted, it is like chocolate candy with molten chocolate, and inside the nuts - so you can imagine the core of the Earth. Convection of the solid mantle of the Earth - very slow, its speed is about 1 centimeter per year; More hot streams go up, coolest - down, and this is the convective movement of the earth's mantle and responsibly for the drift of continents, volcanism, earthquake.
Important question - what is the temperature in the center of the Earth? We know the pressure from seismological models, and the temperature does not give these models. The temperature is determined as follows: we know that the inner core is solid, the external kernel is liquid, and that the core consists of iron. Thus, if you know the melting point of iron at this depth, then you know the kernel temperature at this depth. Experiments were performed, but they gave uncertainty of 2 thousand degrees, and calculations were made, and the calculations put the point on this issue. The melting point of iron on the border of the inner and external kernel was about 6.4 thousand degrees Kelvin. But when geophysics learned about this result, it turned out that this temperature is too large in order to properly reproduce the characteristics of the magnetic field of the Earth - this temperature is too high. And here physicists remembered that actually the kernel is not pure iron, but contains various impurities. What, we still do not know exactly, but among candidates - oxygen, silicon, sulfur, carbon, hydrogen. Variating different impurities, comparing their effects, it was possible to understand that the melting point should be reduced by about 800 degrees. 5600 degrees Kelvin - such a temperature on the border of the internal and external nuclei of the Earth, and this assessment is currently generally accepted. This effect of lowering the temperature of impurities, eutectic decrease in melting point, well known, thanks to this effect, our shoes suffers in winter - the road fell out in order to lower the melting point of snow, and thanks to this, the hard snow is moving into a liquid state, and our shoes suffer from This salty water.
But, perhaps, the strongest example of the same phenomenon is an alloy of Wood - alloy, which consists of four metals, there are bismuth, lead, tin and cadmium, each of these metals has a relatively high melting point, but the effect of mutual decrease in melting point It works so much that Wood alloy melts in boiling water. Who wants to do this experience? By the way, this sample of alloy Wood I bought in Yerevan on the black market, which, probably, will give this experience an additional flavor.
Leite boiling water, and I will keep the alloy of Wood, and you will see how the wood alloy drops will fall into the glass.
Drops fall - everything is enough. It melts at hot water temperatures.
And this effect occurs in the Earth's kernel, due to this, the melting point of the ferrous alloy decreases. But now the next question is: but still the kernel consists of? We know that there is a lot of iron and there are some light elements impurities, we have 5 candidates. We started with the least probable candidates - carbon and hydrogen were considered as followed. I must say that until recently, few people paid attention to these candidates, both were considered unlikely. We decided to check it out. With the employee of Moscow State University, Zulfia Bazhanova, we decided to take up this case, predict stable structures and stable carbides and iron hydrides in the conditions of the land core. We also did it for silicon, where no special surprises were discovered - and for carbon it turned out that those compounds that were considered resistant for many decades, in fact, at the pressure of the nucleus, the land turn out to be unstable. And it turns out that carbon is a very good candidate, in fact alone only by carbon one can explain many properties of the inner core of the Earth perfect, contrary to the previous works. The hydrogen turned out to be a rather poor candidate, alone with hydrogen can not be explained by any property of the land core. Hydrogen may be present in small quantities, but he cannot be the main element-impurity in the Earth's kernel. For hydride hydrodes under pressure, we also found a surprise - it turned out that there is a sustainable connection with the formula that contradicts school chemistry. A normal chemist of hydride hydride formulas will write as FEH 2 and FEH 3, generally speaking, there is still a FEH under pressure, and they have come with this - but the fact that FEH 4 may occur under pressure, has become a real surprise. If our children in the school will write FEH 4 formula, I guarantee that they will get a twice in chemistry, most likely, even a quarter. But it turns out that under pressure the rules of chemistry are violated - and such exotic compounds occur. But, as I said, the gland hydrides are unlikely to matter for the indoors of the Earth, it is unlikely that hydrogen is present there in significant quantities, but carbon is most likely present.
And finally, the last illustration, about the mantle of the Earth, or rather, about the border of the core and mantle, the so-called layer D ", which has very strange properties. One of the properties was the anisotropy of the propagation of seismic waves, sound waves: in the vertical direction and in the horizontal direction of the speed differ significantly. Why is it so? For a long time I could not understand. It turns out that a new structure of magnesium silicate is formed in the layer on the border of the nucleus and mantle of the Earth. We managed to understand this 8 years ago. At the same time, we and our Japanese colleagues have published 2 works in Science and Nature, which proved the existence of this new structure. It can be seen immediately that this structure looks completely different in different directions, and its properties should differ in different directions - including the elastic properties that are responsible for the distribution of sound waves. With the help of this structure, all those physical anomalies were managed to explain and delivered trouble for many years. It was possible to even make several predictions.
In particular, on smaller planets, such as Mercury and Mars, there will be no layer like a layer D ". There is not enough pressure to stabilize this structure. It was also possible to predict that as the land cooling, this layer should grow, because the stability of post-perovskite grows with a decrease in temperature. It is possible that when the Earth was formed, this layer was not at all, and he was born in the early phase of the development of our planet. And all this can be understood due to the predictions of new structures of crystalline substances.
Replica from the hall:Thanks to the genetic algorithm.
Artem Oganov:Yes, although this is the last story about post-perovskite preceded the invention of this evolutionary method. By the way, she came across me for the invention of this method.
Replica from the hall:So 100 years of this genetic algorithm, there they have not yet done.
Artem Oganov:This algorithm was created by me and my graduate student in 2006. By the way, to call it "genetic" incorrectly, the more correct name is "Evlivational". Evolutionary algorithms appeared in the 70s, and they found the use in very many areas of technology and science. For example, cars, ships and airplanes are optimized with the help of evolutionary algorithms. But for each new task, the evolutionary algorithm is completely different. Evolutionary algorithms are not one method, but a huge group of methods, a whole huge area of \u200b\u200bapplied mathematics, and for each new type of tasks you need to invent a new approach.
Replica from the hall:What mathematics? Genetics is.
Artem Oganov:This is not genetics - it is Mathematics. And for each new task you need to invent your new algorithm from zero. And people actually tried to invent evolutionary algorithms and adapt them to predict crystal structures. But they took too literally algorithms from other areas - and it did not work, so we had to create a new method from scratch, and it turned out to be very powerful. Although the region of evolutionary algorithms exists approximately as much as I am at least since 1975, for the prediction of crystalline structures, quite great efforts were required to create a working method.
All these examples that I brought you show, as an understanding of the structure of the substance and the ability to predict the structure of the substance lead to the design of new materials that may have interesting optical properties, mechanical properties, electronic properties. Materials that make up the land of the earth and other planets. In this case, you can solve a whole range of interesting tasks on a computer using these methods. A huge contribution to the development of this method and its application made my employees and more than 1,000 users of our method in different parts of the world. All these people and organizers of this lecture, and you - for your attention - let me warmly thank.
Boris Dolgin: Thank you so much! Thank you very much, Artyom, thank you very much to the organizers who gave us a platform for this version of public lectures, thank you very much, which I supported us in this initiative, I am sure that Artem's research will continue, it means there will be a new material for his lecture. because I must say something from what sounded today, in fact, at the time of previous lectures, in fact, did not exist, therefore it makes sense.
Question from the hall:Tell me, please, how to provide room temperature at a high pressure? Any system of plastic deformation is accompanied by heat generation. You, unfortunately, did not say about it.
Artem Oganov:The fact is that it all depends on how quickly you are compressing. If compression is carried out very quickly, for example, in shock waves, it is necessarily accompanied by heating, sharp compression leads to the growth of temperatures. If you are slow compression, then a sample is sufficiently enough to exchange heat with its environment and come to thermal equilibrium with its medium.
Question from the hall:And your installation made it possible to do?
Artem Oganov:The experiment was not spent by me, I did only calculations and theory. I do not let myself for the experiment on internal censorship. And the experience was carried out in chambers with diamond anvils, where a sample is squeezed between two small diamonds. In such experiments, the sample has so much time to come to the thermal equilibrium that the question does not arise here.
Artem Oganov, one of the most quoted mineralogs of the theoreticals of the world, told us about the computer prediction, which became achievable not so long ago. Previously, this task was not possible to decide because the problem of computer design of new materials includes considered an unresolved problem of crystal structures. But thanks to the efforts of Oganova and his colleagues managed to get closer to this dream and embody her into reality.
Why this task is important: before, new substances were developed for a very long time and with plenty of effort.
Artem Oganov: "Experimentors go to the laboratory. Mix various substances at different temperatures and pressures. Receive new substances. Measure their properties. As a rule, these substances do not pose any interest, rejected. And experimenters are trying again to get a little different substance under other conditions, with a slightly different composition. And so step by step, we overcome many failures, spending your life for this years. It turns out that researchers, in the hope of obtaining one material, spend a huge amount of effort, time, as well as money. This process may take years. It can be a dead end and never lead to the opening of the desired material. But even when he leads to success, this success is given by a very expensive price. "
Therefore, it is necessary to create such a technology that might make error-free predictions. That is, not experimenting in laboratories, but to give the task to the computer to predict what material, with which composition and temperature will have the desired properties under certain conditions. And the computer, turning over numerous options, will be able to answer what kind of chemical composition and which crystal structure will respond to the specified requirements. The result may be such that the desired material does not exist. Or he is not alone.
And then the second challenge arises, the solution of which is not yet: how to get this material? That is, the chemical composition, the crystal structure is understandable, but there is still no possibility to implement it, for example, on an industrial scale.
The main thing is that it is necessary to predict is a crystal structure. Previously, it was not possible to solve this problem, because there are many options for the location of atoms in space. But the overwhelming part does not represent any interest. These embodiments of atoms in space are important, which are sufficiently stable and have the properties needed for researcher.
What these properties are: high or low hardness, electrical conductivity and thermal conductivity and so on. The crystal structure is important.
"If you think, say, about the same carbon, take a look at the diamond and graphite. Chemically this is the same substance. But the properties are completely different. Black super mightmate carbon and transparent super hard diamond, - What determines the difference between them? It is the crystal structure. It is due to her one substance is superhard, the other is super might. One is a conductor of practically metal. Another is a dielectric. "
In order to learn to predict a new material, you must first learn to predict the crystal structure. For this, Ohanov and his colleagues in 2006, an evolutionary approach was proposed.
"In this approach, we are not trying to try out all the infinite many crystal structures. We test it step by step, starting with a small random sample, inside which we rank possible solutions, the worst of which we discard. And from the best we produce subsidiaries. Subsidiaries are made by different mutations or by recombinations - by heredity, where we combine various structural features of the composition from two parents. Of this, a subsidiary is a subsidiary, a child chemical composition, a subsidiary. These subsidiaries are also evaluated. For example, in stability or by the chemical or physical property that interests you. And those that were expressed unfavorable, we discard. Those who promising receive the right to produce offspring. We produce a mutation or heredity of the next generation. "
So step by step, scientists approach the optimal material for them from the point of view of this physical property. The evolutionary approach in this case works as well as the Darwinian theory of evolution, this principle of Yoganov and its colleagues are carried out on a computer when searching for crystalline structures that are optimal from the point of view of this property or stability.
"I can also say (but it's already a little on the verge of hooliganism) that when we carried out to work this method (by the way, the development continues. It was improved more and more), we experimented with different ways of evolution. For example, we tried to produce one child from two parents, but from three or four. It turned out that also, as in life, to optimally produce one child from two parents. One child has two parents - Dad and Mom. Not three, not four, not twenty four. This is optimistic both in nature and on the computer. "
Yoganov patented his method, and now they enjoy almost thousands of researchers around the world and several largest companies, such as Intel, Toyota and Fujitsu. Toyota, for example, according to Oganova, has already invented a new material for lithium batteries that will be used for hybrid cars with the help of this method.
It is believed that the diamond, being a hardness record holder, is the optimal superhard material for all applications. However, this is not the case, because in the gland, for example, it dissolves, and in the oxygen medium at high temperatures, it burns. In general, the search for the material that would be harder diamond, worried humanity for many decades.
"A simple computer calculation that was conducted by my group shows that such a material can not be. In fact, the alternate diamond can be only a diamond, but in nano-crystalline form. Other materials to beat the diamond of hardness in the state. "
Another direction of the Oganova group is the prediction of new dielectric materials that could serve as the basis for super-capacitors for storing electrical energy, as well as for further miniaturization of computer microprocessors.
"This miniaturization actually meets obstacles. Because the existing dielectric materials are poorly kept electrical charges. There are leakage. And further miniaturization is impossible. If we can get a material that is held on silicon, but at the same time has a much higher dielectric constant than the materials we have, we can solve this task. And we have enough serious promotion also in this direction. "
And the last thing, which makes Yoganov, is the development of new drugs, that is, too, their prediction. This is possible due to the fact that scientists have learned to predict the structure and chemical composition of the surface of the crystals.
"The fact is that the surface of the crystal often has a chemical composition differing from the very substance of the crystal. The structure is also very often different. And we found that the surfaces of simple, it would seem inert oxide crystals (such as magnesium oxide) contain very interesting ions (such as ion peroxide). They also contain groups similar to ozone consisting of three oxygen atoms. This explains one extremely interesting and important observation. When a person inhales fine particles of oxide minerals, which seemed to be inert, safe and harmless, these particles play a cruel joke and contribute to the development of lung cancer. In particular, it is known that the carcinogenic substance is asbestos, which is exclusively inert. So, on the surface of this kind of minerals as asbestos and quartz (especially quartz), ions peroxide can be formed, which play a key role in the formation and development of cancer. With the help of our technique, it is also possible to predict the conditions in which the formation of this kind of particles could be avoided. That is, there is hope even to find therapy and warning of lung cancer. In this case, we are talking only about lung cancer. And from a completely unexpected side, the results of our research gave the opportunity to understand, and may even be prevented or healing the lung cancer. "
If sums up, the prediction of crystalline structures can play a key role in the design of materials for both microelectronics and pharmaceuticals. In general, such a technology opens a new path in the technology of the future, I am sure Yogan.
You can read about other directions of the Lab Artemia by reference, but to get acquainted with his book Modern Methods of Crystal Structure Prediction
