REPRODUCTION OF QUANTUM TIGHT-BINDING EFFECTS IN SILICON CLUSTERS BY A 4-BODY CLASSICAL-MODEL

The results obtained by a recently proposed empirical potential for si licon which includes four-body terms are compared with the results of quantum-mechanical tight-binding calculations. In paticular, the groun d-state energy and structure of the Si33 cluster were computed by both methods. By performing an equivalent calculation using only up to thr ee-body interactions we demonstrate that the four-body term is absolut ely necessary in order to achieve good agreement with the quantum meth od.