  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.
