Phase stability, physical properties of rhenium diboride under high pressure and the effect of metallic bonding on its hardness

Abstract

Using first-principles calculations, the elastic constants, thermodynamic property and structural phase transition of rhenium diboride under pressure are investigated by means of the pseudopotential plane-waves method, as well as the effect of metallic bond on its hardness. Eight candidate structures of known transition-metal compounds are chosen to probe for rhenium diboride ReB2. The calculated lattice parameters are consistent with the experimental and theoretical values. Based on the third order Birch–Murnaghan equation of states, the transition pressure Pt between the ReB2–ReB2 and MoB2–ReB2 phases is firstly determinate. Elastic constants, shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature are derived. The single-bonded B–B feather remains in ReB2 compounds. Furthermore, according to Mulliken overlap population analysis, a semiempirical method to evaluate the hardness of multicomponent crystals with partial metallic bond is presented. Both strong covalency and a zigzag topology of interconnected bonds underlie the ultraincompressibilities. In addition, the superior performance and large hardness (39.1GPa) of ReB2–ReB2 indicate that it is a superhard material.