Crystal Structure and Properties of Theoretically Predicted AlB12

Abstract

Aluminum borides have various industrial applications, used in fuels, explosives, abrasives, and as additives to consolidated materials based on boron carbide. The structure of AlB12 is similar to that of boron carbide, including almost regular icosahedrons of boron atoms. The absence of the structure data of some higher aluminum borides and the presence of a large number of reflexes in their diffraction patterns makes the identification of phase compositions very difficult and limits the possibilities of the computer modeling of the AlB12. The crystal structure of AlB12 is usually considered as tetragonal α-AlB12 (space group P43212) and orthorhombic γ-AlB12 (space group P212121) which can be synthesized from high-temperature Al-B melts. In our work, we have performed ab initio optimization of the experimentally observed Yannoni’s AlB12 using GGA-PBE functional and obtained relaxed unit cell parameters and atomic positions. Furthermore, we have predicted three different AlB12 structure candidates obtained as a result of the ICSD data mining. The most favorable structure according to total energy ranking was found in the UB12 structure type, which crystallizes in the cubic space group Fm-3m. Therefore, for the new cubic AlB12, we have calculated mechanical properties on different pressures and made the comparison with available experimental data in the AlB12 system.