Aj. Forsyth et al., DIELECTRIC-MATRIX CALCULATION OF THE VOLUME-PLASMON DISPERSION-RELATION FOR SILICON, Physical review. B, Condensed matter, 54(20), 1996, pp. 14355-14361
Plasmon-band splitting in silicon has been the subject of theoretical
interest recently, since reports of its experimental observation using
coherent inelastic x-ray scattering. The theoretical plasmon-dispersi
on relation can be obtained from dielectric-response theory and knowle
dge of the electronic structure of the solid. In this work the frequen
cy- and wave-vector-dependent dielectric matrix (DM) has been calculat
ed in the random-phase approximation, with a nonlocal empirical pseudo
potential (EPM) electronic band structure. We present results for the
volume-plasmon dispersion relation along high-symmetry directions in t
he first Brillouin zone. Contrary to previous local EPM-based DM calcu
lations, this nonlocal EPM band structure results in excellent agreeme
nt with the experimental plasmon-dispersion anisotropy. In addition, t
hese dispersion results are in better agreement with experiment than p
revious local-density-approximation calculations. Evidence for a weak
approximate to 2-eV band gap is found at the L point. Unlike previous
calculations, the presence of two plasmon resonances is directly obser
vable from the calculated loss function in the Lambda direction.