First-principle Calculations of Optical Properties of LiNbO3

Lithium niobate (LiNbO₃) is one of the most important ferroelectric and nonlinear optical crystals and has many technological applications. But few fundamental theoretical studies on it are reported. The band structure and optical properties of this crystal are calculated within the framework of density functional theory with generalized gradient approximation (DFT-GGA). The results show that the band gap at the G point of brillouin zone is 3.54 eV, which is more close to the experimental value than that from LDA calculations, and that the optical properties of LN crystal, such as the reflectivity and the imaginary part of the dielectric function, are anisotropic along different polarization directions. The relation between electronic structure and optical properties are also discussed