Tw. Josefsson et Ae. Smith, LOCAL-FIELD EFFECTS IN THE HIGH-Q-VECTOR DIELECTRIC RESPONSE OF SI, Australian journal of physics, 46(5), 1993, pp. 635-645
The influence of microscopic or local fields on the full frequency- an
d wavevector-dependent dielectric loss function of Si has been calcula
ted, based on accurate empirical pseudopotential calculations of the e
lectronic structure. It is shown that local-field effects, dramaticall
y significant at optical (q almost-equal-to 0) wavevectors, diminish w
ith increasing magnitude of q to negligible proportions as q approache
s the Brillouin zone boundary. In addition it is shown that the calcul
ated volume-plasmon dispersion relation is improved in comparison with
experimental results by the inclusion of local-field effects.