DISLOCATION AND GRAIN-BOUNDARY ENERGIES IN SI AND GE FROM AN ANHARMONIC BOND CHARGE MODEL

The paper presents calculated line energy values for the reconstructed 60 degrees and 90 degrees glide-set partial dislocations in Si and Ge , formation and migration energy for the reconstructed kink on the rec onstructed 90 degrees partials, and energy data for the symmetric Sigm a = 9 [011] and for two variants of the symmetric Sigma = 11 [011] til t grain boundaries. Criteria are formulated to identify interatomic fo rce field models which are able to provide reliable energy estimates. The anharmonic bond charge (a.bc) model is introduced as an example th at approximately fulfills the basic criteria, i.e., describes well the second and third order elastic constants and the phonon dispersion cu rves. Deviations between energy estimates from the a.bc model and less reliable approaches are discussed. It is shown that in case of the Si gma = 11 [011] tilt grain boundary the a.bc model gives different ener getical ranking for the so-called Sigma = 11A and the Sigma = 11B vari ants in Si and Ge, in agreement with the experimental observations.