INELASTIC PLASMON AND INTERBAND ELECTRON-SCATTERING POTENTIALS FOR SIFROM DIELECTRIC MATRIX CALCULATIONS

Inelastic scattering of electrons in a crystalline environment may be represented by a complex non-Hermitian potential. Complete generalized expressions for this inelastic-electron-scattering-potential matrix, including virtual-inelastic scattering, are derived for outer-shell el ectron and plasmon excitations. The relationship between these express ions and the general anisotropic dielectric-response matrix of the sol id is discussed. These generalized expressions necessarily include the off-diagonal terms representing effects due to departure from transla tional invariance in the interaction. Results are presented for the di agonal band-structure-dependent inelastic and virtual-inelastic scatte ring potentials for Si, from a calculation of the inverse dielectric m atrix in the random-phase approximation. Good agreement is found with experiment as a function of incident energies from 10 eV to 100 keV. A nisotropy effects, and, hence, the interaction delocalization represen ted by the off-diagonal scattering-potential terms are found to be sig nificant below 1 keV.