Electronic states of silicon vacancy. I. Covalent states

Self-consistent generalized valence bond (GVB) and configuration- interaction calculations have been performed for a cluster model of the neutral vacancy in silicon. Three low-lying states (E1,T13,A25) are found to possess one electron in dangling-bond orbitals on each of the four silicon atoms around the defect. Of these three covalent states, the E1 is found to be the ground state with the excitation energies to the T13 and A25 states being 0.17 and 0.60 eV, respectively. The shapes of the GVB orbitals for all three states are found to be quite similar.