New ternary nanolaminated carbide Mo2Ga2C: A first-principles comparison with the MAX phase counterpart Mo2GaC

Abstract

Based on density functional theory and plane-wave pseudopotential total energy method, the structural, mechanical and bonding properties of newly synthesized ternary carbide Mo2Ga2C were investigated. The mechanical properties were explained on the basis of calculated single crystal and polycrystalline elastic properties including Debye temperature and theoretical Vickers hardness. The electronic band structures, total as well as partial densities of states and Mulliken atomic populations were calculated to describe the bonding properties of Mo2Ga2C. All the results for Mo2Ga2C were compared with those of its MAX phase counterpart Mo2GaC. The extra Ga-layer in Mo2Ga2C causes a significant reduction of most of the elastic constants and moduli, Poisson’s and Pugh’s ratios, elastic anisotropy factors and the strength of directional bonding. Mo2Ga2C is more resistant to thermal shock than Mo2GaC and possesses comparatively low thermal conductivity. Due to the extra Ga-layers, the DOS at the Fermi level reduces slightly and the Mo–C bond becomes more covalent in Mo2Ga2C than that of Mo2GaC. In addition, the extra Ga-layer reduces the hardness of Mo2Ga2C and makes it relatively soft and easily mechinable compared to Mo2GaC.