The relaxation of the H-terminated diamond (C), Si and Ge (1 1 1) surfaces

Abstract

The relaxation of the H-terminated diamond (C), Si and Ge (1 1 1) surfaces are investigated using the complete neglect of differential overlap (CNDO) method. It is found that there is no relaxation in diamond surfaces. However, for Si (1 1 1) surfaces, the calculation shows that there is a 3.6% contraction of the 1st layer and 2.6% expansion of the 2nd layer; for Ge (1 1 1), the 1st layer contracted substantially. We conclude that the redistribution of the charge density from atomic S-orbitals to P-orbitals is the main mechanism for the strengthening and shortening of the Ge-Ge back bond.