Exchange and correlation effects beyond the LDA on the dielectric function of silicon

The macroscopic dielectric function of crystalline silicon is calculated within density-functional theory, considering exchange and correlation effects beyond the local-density approximation. Reproposing an original idea of Hohenberg and Kohn, we consider a functional based on the exchange and correlation kernel of the homogeneous electron gas, K(xc)(HEG). The same kernel is used in:the evaluation of the dielectric matrix, keeping local-held effects into account. The results, compared with those obtained in the local-density approximation, show a limited reduction of the well-known overestimation of the macroscopic dielectric constant. Results obtained for optical and energy loss spectra are also presented. [S0163-1829(99)00344-6].