First-principles study of the structural,elastic,and optical properties for Sr0.5Ca0.5TiO3

A detailed theoretical study of the structural,elastic,and optical properties for Sr0.5Ca0.5TiO3is carried out by firstprinciples calculations.The band structure exhibits a direct bandgap of 2.08 eV at theΓpoint in the Brillouin zone.The bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio are derived based on the calculated elastic constants.The bulk modulus B=153 GPa and shear modulus G=81GPa are in good agreement with available experimental data.Poisson’s ratioν=0.275 suggests that Sr0.5Ca0.5TiO3should be classified as being a ductile material.Using the electronic band structure and density of states,we analyze the interband contribution to the optical properties.The real and imaginary parts of the dielectric function,as well as the optical properties such as the optical absorption coefficient,refractive index,extinction coefficient,and energy-loss spectrum are calculated.The static dielectric constantε1(0)and the refractive index n(0)are also investigated.