Structural stability of MoB up to 25 GPa: experiment and computation

Abstract

In this work we report both experimental and computational study on the structural stability of MoB under pressure. The single phase MoB with tetragonal structure (I41/amd) having lattice parameters a = 3.109(2) Ǻ and c = 16.936(7) Ǻ was studied using a Mao-Bell type diamond anvil cell (DAC) to collect high pressure x-ray diffraction (HPXRD) data in angle dispersive x-ray mode up to a pressure of ∼25 GPa. The tetragonal structure remains stable up to 25 GPa. The a-axis shows lower compressibility than the c-axis. The anisotropy behaviour in the compressibility is discussed taking cue from the bond alignment in the structure. Compressibility behaviour of MoB is also compared to WB with regard to their electronic structure and charge distribution. The charge density plots as a function of pressure reveal strong covalent bond along a-axis and weak covalent bond between Mo-B. The high pressure XRD data yields a bulk modulus of 311 GPa which agrees well with the computed value of ∼304 GPa.