First-principles calculations of hydrostatic pressure effects on the structural, elastic and thermodynamic properties of cubic monocarbides XC (X = Ti, V, Cr, Nb, Mo, Hf)

Abstract

Six transition metal monocarbides (TiC, VC, CrC, NbC, MoC, HfC) with the rock-salt structure were chosen for a detailed comparative ab initio study of their structural, electronic, elastic, and thermodynamic properties at ambient and elevated up to 50 GPa hydrostatic pressures. Special attention was paid to the relation between the elastic and bonding properties and the number of valence electrons in each compound. Elastic anisotropy of the considered carbides was analyzed; the directions in the crystal lattice corresponding to the greatest and smallest Young's moduli values were identified. The calculated values of the elastic constants were used for further estimations of the Debye temperatures, Grüneisen parameters, specific heat capacities and linear coefficients of thermal expansion. Comparison of the calculated results with available experimental and theoretical data for TiC, VC, NbC, HfC yielded good agreement. The specific heat capacities and thermal expansion coefficients for CrC and MoC were calculated for the first time, to the best of the authors' knowledge.