Induced polarization charge density and microscopic local field for a covalent semiconductor

A model calculation of the static macroscopic dielectric function is presented for diamond in which the consequence of the localised and plane wave features of the band structure on the polarizability are separated. Microscopic local field and polarization charge density induced by an uniform external field are analyzed in real space. Although the macroscopic dielectric function is essentially intensitive to small changes in the parameters of the model, microscopic quantities can be rather sensitive suggesting that one should be carefull in constructing a microscopic dielectric matrix to be used in calculating, for instance, phonon frequencies.