Pressure dependent elastic, electronic, superconducting, and optical properties of ternary barium phosphides (BaM2P2; M = Ni, Rh): DFT based insights

Abstract

Density functional theory based investigations of structural, elastic, electronic band structure, and optical properties of superconducting ternary phosphides (BaM2P2; M = Ni, Rh) have been carried out. Calculated ambient condition properties are compared with experimental and theoretical results, where available. Pressure dependent electronic density of states at the Fermi level, N(EF), and the Debye temperature, θD, have been explored and their effect on the superconducting transition temperature have been disclosed. N(EF) shows nonmonotonic pressure dependence in BaNi2P2. Pressure dependence of N(EF) for BaRh2P2, on the other hand, is systematic. Pressure dependence of N(EF) affects superconducting transition temperature significantly. Debye temperature increases with increasing pressure. Variation of optical parameters with photon energy show metallic behavior complementing the features of electronic band structure calculations. Absorption coefficient of BaNi2P2 exhibits strong optical absorption in ultraviolet region, while BaRh2P2 absorbs photons over a wider energy band including the entire visible range. Reflectivity spectra for both BaNi2P2 and BaRh2P2 reveal that they are strong reflectors of visible light and BaNi2P2 in particular holds significant promise to be used as coating material to reduce solar heating.