Ab initiostatic dielectric matrices from the density-functional approach. II. Calculation of the screening response in diamond, Si, Ge, and LiCl

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Abstract
The density-functional approach with ab initio pseudopotentials has been used to calculate the static dielectric matrices for diamond, Si, Ge, and LiCl. The dielectric matrices for a regular sample of points in the Brillouin zone are used to calculate the screening response of the crystals to external perturbations. The perturbations considered are a constant external electric field and an added point charge at various locations in the unit cell. Through these examples, the local fields in the screening are illustrated and a qualitative picture of the role of exchange and correlation (included in the local-density approximation) is obtained. Local fields in semiconductors and insulators are found both to be quantitatively important and to alter the qualitative features of the screening response.