Scientists from Russia, Germany and Sweden have jointly proved the possibility of the existence of substances that are unrealistic from the point of view of the usual understanding of the laws of chemistry. By subjecting the beryllium compound to pressure hundreds of thousands of times higher than atmospheric pressure, the researchers achieved the transformation of the crystal structure of the material to five and six oxygen atoms around the beryllium atom, although it was previously believed that the maximum possible number does not exceed four.
Imagine that you have a mountain of cubes in front of you, and you are going to build something from them, - the authors of the study describe their work. - you can collect a variety of different structures, but still their number is limited due to the form of "building materials", because they can only connect to each other in a certain way. Now imagine that you have the opportunity to change the shape of these cubes - to stretch them, add faces, in a word, modify them so that the number of possible combinations of the resulting "building materials" increases countless times.
The cubes in question are nothing more than elements of the crystal structure of materials, modifying which, you can “reward” materials with fundamentally new properties. But certain transformations are impossible within the framework of the usual ideas.
“We worked with herlbutite, a form of beryllium compound with the chemical formula CaBe2P2O8. Under classical conditions, it has a tetrahedral structure - beryllium forms tetrahedral pyramids with oxygen atoms, and until recently it was believed that this is the maximum possible coordination of beryllium. However, our colleagues from Germany conducted an experiment, as a result of which it became clear that the crystal structure can be rearranged. During the experiment, the material was placed in a diamond anvil, where it was exposed to ultrahigh pressures. So, at a pressure of 17 GPa (170 thousand terrestrial atmospheres), the number of oxygen atoms surrounding beryllium increased to five, and at a pressure of 80 GPa (800 thousand terrestrial atmospheres), the crystal was rearranged so that this number increased to six. This is an incredible resultby no one and never introduced before. That is why he also needed a theoretical justification, which we worked on independently on our supercomputer,”says Professor Igor Abrikosov.
Theoretical modeling of the results of the experiment was carried out by scientists from NUST MISIS in record time - in just one month. To solve the Dirac equation describing the state of electrons in matter, with the given variables, all the computing power of the supercomputer cluster of the laboratory "Modeling and development of new materials" was used. The calculation results almost completely coincided with the experimental results - the differences are minimal, and are within the acceptable range of error.
The results of the experiment and its theoretical justification were presented by scientists in the journal Nature Communications.
Sergey Sysoev
