First-Principles Study of the Elastic, Hardness and Electronic Properties of MoAlB under High Pressure

Abstract

The structure, elastic and electronic properties of MoAlB have been studied under high pressure by using first principles. The optimized lattice parameters, elastic constants, bulk moduli, and shear moduli agree well with experimental and other theoretical values. The relationships of the lattice constants with pressure indicated an anisotropic behavior. The calculated elastic constants satisfy the mechanical stability conditions. Our calculated Vickers hardness of MoAlB is 11.56 GPa, which agrees with the experimental data and confirms its having a relatively softer nature than the other borides. The Cauchy pressure, the Poisson’s ratio and the G/B value suggest that MoAlB is a brittle solid under ambient conditions, but the brittleness decreases with increasing pressure. The band structure and the density of states reveal the metallic feature of MoAlB, and the energy levels shift toward both sides of the Fermi level with increasing pressure. The Mulliken population and density of states suggest a mixture bonding nature of covalence and metallicity in MoAlB.