Polarization-dependent far-infrared reflectivity measurements were carried out on single crystals of anatase ${\mathrm{TiO}}_2$ . The results were analyzed to yield the dielectric dispersion properties of anatase in the lattice fundamentals regime. The frequencies (in ${\mathrm{cm}}^{\mathrm{-}1}$ ) of the transverse optical (TO) and longitudinal optical (LO) zone-center phonons were determined to be 367(755) for the TO (LO) of the ${\mathrm{A}}_{2\mathrm{u}}$ mode, 262(366) and 435(876) for the ${\mathrm{E}}_{\mathrm{u}}$ modes. The large TO-LO splittings were used to estimate effective charges.

DOI:https://doi.org/10.1103/PhysRevB.55.7014