Lithium niobate-tantalate mixed crystals electronic and optical properties calculated from first principles

The electronic and optical properties of the mixed-crystal system lithium niobate-tantalate has been calculated from first principles. Based on density functional theory we calculate the electronic properties including quasiparticle effects within the GW approach. The optical response including electron-hole attraction effects is obtained from the solution of the Bethe-Salpeter equation. While the band gap increase with increasing tantalum content and shows some bowing, a nearly linear dependence of the optical birefringence on the stochiometry is calculated.