A NOVEL METHOD FOR COMPUTING BOND BOND INTERACTIONS OF LARGE SYSTEMS

A method for rapidly computing electric dipolar susceptibilities of la rge systems such as semiconductor surfaces is given. Bond polarisabili ties and bond-bond interactions are calculated by an ab initio techniq ue. Bond interactions are also calculated by a point-dipole model wher e bond dipoles are assumed to be point dipoles located at the bond mid points, interacting by point-dipole electric fields. The feasibility o f applying the method to large systems depends on the fact that point- dipole-bond interactions agree with ab initio computed interactions fo r bonds further than two bond distances apart so that only a few bond interactions need be calculated from first principles.