First-principles calculation of the electronic, dielectric, and dynamical properties ofCaF2

Calcium fluoride is a prototypical very large band-gap material, with applications in far-ultraviolet optics. We study the electronic, dielectric, and vibrational properties of ${\mathrm{CaF}}_2$ from first principles, using density-functional theory. The phonon band structure is well reproduced with standard pseudopotentials, except for one optical $T_{1u}$ mode near $\Gamma$ and X. However, the calculated dielectric properties are very poor. Improving the quality of the dielectric constants of the crystal requires a pseudopotential for Ca with additional semicore electrons. We perform a detailed analysis of the static and dynamical charges, as well as the interatomic force constants.