First-principles study of the structural, elastic, and optical properties for Sr_0.5Ca_0.5TiO₃

A detailed theoretical study of the structural, elastic, and optical properties for Sr_0.5Ca_0.5TiO₃ is carried out by first-principles calculations. The band structure exhibits a direct bandgap of 2.08 eV at the Γ point 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 ratio ν=0.275 suggests that Sr_0.5Ca_0.5TiO₃ should 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 constant ε₁(0) and the refractive index n(0) are also investigated.