An international team of scientists jointly with Professor Artem Oganov of Skoltech and the Moscow Institute of Physics and Technology report the chemical composition, crystal structure and properties of Na₂B₃₀? a compound that remains stable at standard conditions and has long been the subject of heated debate. The results of the study were published inPhysical Review B.

　　Boron is a unique element capable of forming complex crystal modifications, all of which are super-hard. Moreover, boron and metal compounds ? borides ? often have highly complex chemical compositions and crystal structures that cannot always be uniquely determined through experiment. Many borides display remarkable features of superhard, superconducting, orthermoelectric materials.

　　In the paper published inPhysical Review B, the scientists looked at sodium borides at standard conditions. Using Oganov's USPEX structure predictor, they proved that Na₂B₃₀is stable and Na₂B₂₉is not, and finally reconciled the research teams arguing about which formula is right ? Na₂B₃₀or Na₂B₂₉. It was demonstrated that adding a single atom has a dramatic impact on both the stability and electronic properties, transforming a metal into a semiconductor and making the material much harder. The compound is potentially super-hard and can exist at standard conditions. Moreover, the researchers proposed a newcrystal structureboasting higher stability and the same consistency with the experimental data as compared to its earlier version.

　　"This study may compete with a detective novel in the number of mysteries to puzzle out. It turns out that everyone had wrong ideas, whether of the formula or thestructure. What always surprises me in such stories is that we keep talking about the 21st century with its advanced science and engineering and virtually unlimited capabilities, but sometimes have a vague idea about a substance under normal conditions. It is good to remember that such substances can have highly interesting technological applications," said Oganov.

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　　More information:Xin-Ling He et al. Predicting the ground-state structure of sodium boride,Physical Review B(2018).DOI: 10.1103/PhysRevB.97.100102　　

　　Journal reference:Physical Review B