Electron-phonon interaction in a shell-model crystal

Abstract

Electrostatic interaction of an excess electron with a shell-model crystal is assumed. The electron-phonon Hamiltonian is derived in the harmonic approximation for the large polaron. The screening potential for the electron arising from shell motion is obtained and discussed for adiabatic, non-adiabatic and intermediate electron-shell interaction. The screening potential arising from core motion is illustrated by a perturbative treatment of electron-phonon interaction in the adiabatic approximation. The mathematical structure of the self-consistent field produced by these screening effects is compared to that of the ion-size correction. Static lattice distortion, associated with self-trapping or a lattice defect, is introduced and its effects on shell screening on the electron-phonon interaction are discussed. Finally, the F-centre is used to illustrate the effect of a lattice defect on shell screening.