Computer design of new materials
Artem Oganov, one of the most cited mineralogical theorists of the world, told us about a computer prediction, which not so long ago was achievable. Previously, this task could not be solved because the problem of computer-aided design of new materials includes the problem of crystal structures that was considered unsolvable. But thanks to the efforts of Oganov and his colleagues managed to get closer to this dream and make it a reality.
Why this task is important: before, new substances were developed for a very long time and with a lot of effort.
Artyom Oganov: “Experimenters go to the laboratory. Mix different substances at different temperatures and pressures. Get new substances. Measure their properties. As a rule, these substances are of no interest, are rejected. And the experimenters are trying again to get a slightly different substance under different conditions, with a slightly different composition. And so, step by step, we overcome many failures, spending on it the years of our lives. It turns out that researchers, hoping to get one material, spend a huge amount of effort, time, and also money. This process can take years. It can be a dead end and never lead to the discovery of the desired material. But even when it leads to success, this success comes at a very high price. ”
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Therefore, it is necessary to create such a technology that could make unmistakable predictions. That is, not to experiment in laboratories, but to give the computer a task to predict what material, with what composition and temperature it will have the necessary properties under certain conditions. And the computer, going through numerous options, will be able to give an answer, which chemical composition and which crystal structure will meet the specified requirements. The result may be such that the desired material does not exist. Or he is not one.
And then there is the second problem, the solution of which is not yet: how to get this material? That is, the chemical composition, the crystal structure is understandable, but so far there is no possibility to implement it, for example, on an industrial scale.
The main thing that needs to be predicted is the crystal structure. Previously, it was not possible to solve this problem, because there are many options for the arrangement of atoms in space. But the overwhelming part of them is of no interest. Important are the variants of the arrangement of atoms in space, which are sufficiently stable and have the necessary properties for the researcher.
What are these properties: high or low hardness, electrical conductivity and thermal conductivity, and so on. The crystal structure is important.
“If you think about, say, the same carbon, take a look at the diamond and graphite. Chemically it is the same substance. But the properties are completely different. Black super soft carbon and transparent superhard diamond - what makes the difference between them? It is a crystal structure. It is thanks to her that one substance is superhard, the other is super-soft. One is practically a metal conductor. The other is a dielectric. ”
In order to learn how to predict new material, one must first learn how to predict the crystal structure. For this, Oganov and his colleagues in 2006 proposed an evolutionary approach.
“In this approach, we are not trying to test the entire infinite number of crystal structures. We will try it step by step, starting with a small random sample, within which we rank the possible solutions, the worst of which we discard. And from the best we produce child variants. Child variants are made by different mutations or by recombination - by heredity, where, from two parents, we combine different structural features of the composition. This results in a subsidiary structure - a subsidiary material, a subsidiary chemical composition, a subsidiary structure. These child formulations are then also evaluated. For example, on stability or on that chemical or physical property which interests you. And those that were ranked unprofitable, we discard. Those that are promising, get the right to produce offspring. By mutation or heredity, we produce the next generation. ”
So step by step, scientists are approaching the material that is optimal for them in terms of a given physical property. The evolutionary approach in this case works in the same way as the Darwinian theory of evolution; this principle is carried out on a computer by Oganov when searching for crystal structures that are optimal from the point of view of a given property or stability.
“I can also say (but this is already a little on the verge of hooliganism) that when we worked on 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 not from two parents, but from three or four. It turned out that, just as in life, it is optimal to produce one child from two parents. One child has two parents - dad and mom. Not three, not four, not twenty-four. This is the optimum both in nature and on the computer. ”
Oganov patented his method, and now it is used by almost thousands of researchers around the world and several major companies, such as Intel, Toyota and Fujitsu. Toyota, for example, according to Oganov, has been using this method for some time to invent a new material for lithium batteries that will be used for hybrid cars.
It is believed that the diamond, as a champion in hardness, is the optimal superhard material for all applications. However, this is not the case because, for example, it dissolves in the gland and burns in an oxygen environment at high temperature. In general, the search for material that would be harder than diamond, has worried mankind for many decades.
“A simple computer calculation, which was carried out by my group, shows that there can be no such material. In fact, diamond can only be harder than diamond, but in a nano-crystalline form. Other materials beat diamond by hardness or in condition. ”
Another direction of the Oganov group is the prediction of new dielectric materials, which 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 available dielectric materials withstand electric charges rather poorly. There is a leak. 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, then we can solve this problem. And we have quite serious progress in this direction as well. ”
And the last thing Oganov does is the development of new drugs, that is, their prediction too. This is possible due to the fact that scientists have learned to predict the structure and chemical composition of the surface of crystals.
“The fact is that the surface of a crystal often has a chemical composition that differs from the substance of the crystal itself. The structure is also very often very different. And we found that the surfaces of simple, seemingly inert oxide crystals (such as magnesium oxide) contain very interesting ions (such as ion peroxide). They also contain ozone-like groups of three oxygen atoms. This explains one extremely interesting and important observation. When a person inhales fine particles of oxide minerals that are seemingly 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 extremely inert. So, on the surface of such minerals as asbestos and quartz (especially quartz) peroxide ions can be formed, which play a key role in the formation and development of cancer. Using our technique, we can also predict the conditions under which the formation of such particles could be avoided. That is, there is hope even to find therapy and prevention of lung cancer. In this case, we are talking only about lung cancer. And from a completely unexpected side, the results of our research made it possible to understand, and maybe even prevent or cure lung cancer. ”
If it sums up, the prediction of crystal structures can play a key role in the design of materials for both microelectronics and pharmaceuticals. In general, this technology opens up a new path in the technology of the future, Oganov is sure .
You can read about other areas of Artem’s laboratory here , and read his book Modern Methods of Crystal Structure Prediction here.
Why this task is important: before, new substances were developed for a very long time and with a lot of effort.
Artyom Oganov: “Experimenters go to the laboratory. Mix different substances at different temperatures and pressures. Get new substances. Measure their properties. As a rule, these substances are of no interest, are rejected. And the experimenters are trying again to get a slightly different substance under different conditions, with a slightly different composition. And so, step by step, we overcome many failures, spending on it the years of our lives. It turns out that researchers, hoping to get one material, spend a huge amount of effort, time, and also money. This process can take years. It can be a dead end and never lead to the discovery of the desired material. But even when it leads to success, this success comes at a very high price. ”
')
Therefore, it is necessary to create such a technology that could make unmistakable predictions. That is, not to experiment in laboratories, but to give the computer a task to predict what material, with what composition and temperature it will have the necessary properties under certain conditions. And the computer, going through numerous options, will be able to give an answer, which chemical composition and which crystal structure will meet the specified requirements. The result may be such that the desired material does not exist. Or he is not one.
And then there is the second problem, the solution of which is not yet: how to get this material? That is, the chemical composition, the crystal structure is understandable, but so far there is no possibility to implement it, for example, on an industrial scale.
Prediction technology
The main thing that needs to be predicted is the crystal structure. Previously, it was not possible to solve this problem, because there are many options for the arrangement of atoms in space. But the overwhelming part of them is of no interest. Important are the variants of the arrangement of atoms in space, which are sufficiently stable and have the necessary properties for the researcher.
What are these properties: high or low hardness, electrical conductivity and thermal conductivity, and so on. The crystal structure is important.
“If you think about, say, the same carbon, take a look at the diamond and graphite. Chemically it is the same substance. But the properties are completely different. Black super soft carbon and transparent superhard diamond - what makes the difference between them? It is a crystal structure. It is thanks to her that one substance is superhard, the other is super-soft. One is practically a metal conductor. The other is a dielectric. ”
In order to learn how to predict new material, one must first learn how to predict the crystal structure. For this, Oganov and his colleagues in 2006 proposed an evolutionary approach.
“In this approach, we are not trying to test the entire infinite number of crystal structures. We will try it step by step, starting with a small random sample, within which we rank the possible solutions, the worst of which we discard. And from the best we produce child variants. Child variants are made by different mutations or by recombination - by heredity, where, from two parents, we combine different structural features of the composition. This results in a subsidiary structure - a subsidiary material, a subsidiary chemical composition, a subsidiary structure. These child formulations are then also evaluated. For example, on stability or on that chemical or physical property which interests you. And those that were ranked unprofitable, we discard. Those that are promising, get the right to produce offspring. By mutation or heredity, we produce the next generation. ”
So step by step, scientists are approaching the material that is optimal for them in terms of a given physical property. The evolutionary approach in this case works in the same way as the Darwinian theory of evolution; this principle is carried out on a computer by Oganov when searching for crystal structures that are optimal from the point of view of a given property or stability.
“I can also say (but this is already a little on the verge of hooliganism) that when we worked on 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 not from two parents, but from three or four. It turned out that, just as in life, it is optimal to produce one child from two parents. One child has two parents - dad and mom. Not three, not four, not twenty-four. This is the optimum both in nature and on the computer. ”
Oganov patented his method, and now it is used by almost thousands of researchers around the world and several major companies, such as Intel, Toyota and Fujitsu. Toyota, for example, according to Oganov, has been using this method for some time to invent a new material for lithium batteries that will be used for hybrid cars.
Diamond problem
It is believed that the diamond, as a champion in hardness, is the optimal superhard material for all applications. However, this is not the case because, for example, it dissolves in the gland and burns in an oxygen environment at high temperature. In general, the search for material that would be harder than diamond, has worried mankind for many decades.
“A simple computer calculation, which was carried out by my group, shows that there can be no such material. In fact, diamond can only be harder than diamond, but in a nano-crystalline form. Other materials beat diamond by hardness or in condition. ”
Another direction of the Oganov group is the prediction of new dielectric materials, which 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 available dielectric materials withstand electric charges rather poorly. There is a leak. 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, then we can solve this problem. And we have quite serious progress in this direction as well. ”
And the last thing Oganov does is the development of new drugs, that is, their prediction too. This is possible due to the fact that scientists have learned to predict the structure and chemical composition of the surface of crystals.
“The fact is that the surface of a crystal often has a chemical composition that differs from the substance of the crystal itself. The structure is also very often very different. And we found that the surfaces of simple, seemingly inert oxide crystals (such as magnesium oxide) contain very interesting ions (such as ion peroxide). They also contain ozone-like groups of three oxygen atoms. This explains one extremely interesting and important observation. When a person inhales fine particles of oxide minerals that are seemingly 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 extremely inert. So, on the surface of such minerals as asbestos and quartz (especially quartz) peroxide ions can be formed, which play a key role in the formation and development of cancer. Using our technique, we can also predict the conditions under which the formation of such particles could be avoided. That is, there is hope even to find therapy and prevention of lung cancer. In this case, we are talking only about lung cancer. And from a completely unexpected side, the results of our research made it possible to understand, and maybe even prevent or cure lung cancer. ”
If it sums up, the prediction of crystal structures can play a key role in the design of materials for both microelectronics and pharmaceuticals. In general, this technology opens up a new path in the technology of the future, Oganov is sure .
You can read about other areas of Artem’s laboratory here , and read his book Modern Methods of Crystal Structure Prediction here.
Source: https://habr.com/ru/post/204220/
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