First-principles study of the dielectric properties and infrared reflectance spectrum of

Yttrium oxide is an important laser and infrared optical material. The structural, vibrational and dielectric properties of Y 2O3 are calculated from first principles using the plane-wave pseudopotential method. The dielectric permittivity tensors, infrared-active phonon frequencies at the Brillouin zone center and the LO/TO splitting are reported within the framework of density functional perturbation theory. Contributions to the static dielectric constant from each infrared-active mode are presented. It is shown that Y 2O3 has an electronic dielectric constant larger than that of the lattice contributions. Dielectric, refractive index, extinction coefficient and infrared reflectance spectra of Y 2O3 are given, and the figures suggest that Y 2O3 presents good transmission properties in the spectrum range above 800 cm−1 or below 400 cm−1.