Dielectric Matrix for Copper

The static dielectric function of copper is evaluated for three principal directions of q , [1, 0, 0], [1, 1, 0], and [1, 1, 1], on the basis of the realistic model. The energy spectra and the wave functions are determined by APW method with the Chodrow potential. The magnitude of the diagonal elements of the dielectric matrix is somewhat larger than the corresponding value of the electron gas owing to the contribution from the d-bands. The non-diagonal elements of the dielectric matrix are also calculated. Some of them are not very small as compared to the diagonal terms.