Application of time-dependent density-functional theory to the dielectric function of various nonmetallic crystals

The dielectric function of a range of nonmetallic crystals of various lattice types is studied by means of a real-space and full-potential time-dependent density-functional method within the adiabatic local-density approximation. Results for the dielectric constant epsilon(infinity) (at optical frequencies) are given for crystals in the sodium chloride, the fluoride, the wurtzite, the diamond, and the zinc-blende lattice structure. The frequency-dependent dielectric function epsilon(omega) for the crystals in the diamond and zinc-blende lattice structure are also presented. We compare our calculated results with experimental data and other theoretical investigations. Our results for the dielectric constants epsilon(infinity) and the dielectric functions epsilon(omega) are in good agreement with the experimental values. The accuracy of the results is comparable to the one which is commonly found for time-dependent density-functional theory calculations on molecular systems. On average we find a deviation of 4-5 % from experiment for the group TV and m-V compounds in the wurtzite, zinc-blende and diamond lattice structure, 8-9 % for the II-VI and I-VII compounds in the zinc-blende and sodium chloride lattice structure, and up to 14% deviation for the fluoride lattice structure. The spectral features of the dielectric functions epsilon(omega) appear in the calculations at somewhat too low energies compared to experiment.