Structural, anisotropic and thermodynamic properties of boron carbide: First principles calculations

Abstract

The structural, mechanical, electronic properties of the potentially superhard P4₂/mnm-BC have been investigated by using the density functional theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation and the local density approximation. The elastic constants, bulk modulus, shear modulus, Young’s modulus, B/G ratio and Poisson’s ratio for BC at various pressures have been investigated. The elastic anisotropy under pressure from 0 GPa to 100 GPa has been studied. The elastic anisotropy of Young’s modulus, shear modulus, and Poisson’s ratio show that P4₂/mnm-BC exhibits a large anisotropy and the elastic anisotropy increases with increasing pressure. Electronic structure studies show that P4₂/mnm-BC is a conductor. Using the quasi-harmonic Debye model, the thermodynamic properties of P4₂/mnm-BC have also been investigated. The variation of the thermal expansion, isothermal bulk modulus, Debye temperature, Grüneisen parameter, and heat capacity with pressure and temperature have been obtained systematically.