Structural parameters, electronic structure and linear optical functions of LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler alloys

Ab initio calculations based on density functional theory were performed to determine the structural parameters of the LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler compounds and verify their thermodynamic stability in an orthorhombic structure as well as to predict their electronic and optical properties. The predicted electronic band structures show that LuVCo2Sb2, LuNbCo2Sb2, and LuTaCo2Sb2 are semiconductors with indirect bandgaps of 0.728, 0.845, and 0.898 eV, respectively. The effective masses calculated at the valence band maximum at the conduction band minimum show a strong anisotropy. It can be seen that electrons are lighter than holes. The nature of the electronic states involved in the formation of the energy bands has been determined thanks to the density of states calculations. The character of chemical bonds was analyzed through the charge density dis-tribution map. Linear optical functions, namely complex dielectric function, absorption coefficient, optical reflectivity and refractive index, were calculated for all compounds in an energy range up to 20 eV. The calculated optical spectra exhibit a noticeable anisotropy. The compounds under consideration are characterized by strong absorption of incident electromagnetic radiation in a wide energy range.