Cluster calculations of C and Si vacancies in cubic SiC were performed for charge states of +1, 0 and -1 and possible spin states. Density functional theory was used, together with the B3LYP exchange-correlation functional and a Gaussian basis set applied to 52- and 70-atom clusters. Calculations of hyperfine coupling parameters for atoms of the first and second shells of vacancies were performed as being suitable for a comparison with

electron paramagnetic resonance data. Test calculations were performed in order to check the validity of applied approximations, and a reasonable agreement between calculated and experimental data was obtained. The ground spin-state and the defect point-symmetry, for all of the above charge states, were determined together with the hyperfine parameters for atoms of the first and second shells. In the ground state, spins of VC-, VSi- and VSi+ had values of S = 3/2, but of S = 1 for VC0 and VSi0 and S = ½ for VC+. Optimization of the geometry led to a minimum having the Td symmetry only for VC-, VSi- and VSi+ centers. At the same time, the VSi0 and VC+ defects had D2d symmetry, while VC0 had C3V symmetry. All of the considered charge states of the C vacancy exhibited markedly stronger hyperfine interactions with nearest and next-nearest neighbors as compared with the Si vacancy.

Symmetry, Spin State and Hyperfine Parameters of Vacancies in Cubic SiC. T.T.Petrenko, T.L.Petrenko, V.Y.Bratus, J.L.Monge: Applied Surface Science, 2001, 184[1-4], 273-7