An ab initio study of the structural, elastic, electronic, optical properties and phonons of the double perovskite oxides Sr2AlXO6 (X=Ta, Nb, V)

We report ab initio density functional theory calculations of the structural, elastic, electronic and optical properties of the double perovskite oxides Sr2AlXO6 (X=Ta, Nb, V). We have predicted a direct Г–Г band gap in Sr2AlXO6 (X=Ta, Nb) and an indirect Г–X band gap for Sr2AlVO6. The fundamental band gap increases linearly when the pressure is enhanced in the range 0–20 GPa. The frequency dependent of complex dielectric function, absorption, reflectivity and electron energy loss function were investigated in the range 0–40 eV. Features such as lattice constant, bulk modulus, elastic constants, band structure, total and local densities of states have been computed.