High pressure mediated physical properties of Hf2AB (A = Pb, Bi) via DFT calculations

Abstract

Using density functional theory (DFT), the structural, mechanical, electronic, thermal, and optical properties of Hf2AB (A = Pb, Bi) borides were studied, considering the pressure effect up to 50 GPa. The lattice constants were found to be decreased with increasing pressure wherein the lattice constants at 0 GPa agree well with the reported values. The stability (mechanical and dynamical) of the titled compounds at different pressures was checked. The mechanical behavior was disclosed considering the bulk modulus, shear modulus, Youngs modulus, Pugh ratio, Poissons ratio, and hardness parameter at different pressures. Pugh and Poisson ratios were used to assess the brittleness and ductility of the titled borides. The anisotropic nature of mechanical properties was studied by calculating different indices and plotting 2D and 3D projections of the elastic moduli. The electronic properties were revealed by calculating the band structure, density of states, and charge density mapping at different pressures, wherein the anisotropic nature of the electronic conductivity was noted. We studied the Debye temperature, minimum thermal conductivity, Gruneisen parameter, and melting temperature of the titled borides at different pressures; the results revealed the improvement of the mentioned properties with rising pressure. The important optical constants to disclose the possible relevance in application purposes were investigated; a little pressure effect was noted. The thermal properties suggest that the titled borides could be used as thermal barrier coating (TBC) materials while the reflectivity spectra revealed their suitability to be used as cover materials for protection from solar heating.