Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory

The optical properties of pristine and titanium-doped ${\mathrm{LiNbO}}_3$ are modeled from first principles. The dielectric functions are calculated within time-dependent density-functional theory, and a model long-range contribution is employed for the exchange-correlation kernel in order to account for the electron-hole binding. Our study focuses on the influence of substitutional titanium atoms on lithium sites. We show that an increasing titanium concentration enhances the values of the refractive indices and the reflectivity.