Distortion of atoms around the neutral vacancy in a Si crystal

Abstract:

The single-particle electronic structure of a neutral lattice vacancy in a Si crystal is treated theoretically within the 16-atom supercell using the conventional tight-binding approximation. The physical mechanism leading to a spontaneous symmetric and tetragonal displacement of atoms surrounding a vacancy is discussed in detail. The elastic response of the lattice is calculated using the Keating valence force model applied to the cluster contained 441 atoms. The directions and amplitudes of atomic displacements are strongly symmetry-dependent. The amplitudes decrease with the distance R from the vacancy, approximately, as R^-2, independently of the distortion symmetry. The influence of the vacancy defects on the lattice parameter is considered and estimated.