Papers by Author: W.V.M. Machado

Abstract: We carried out a theoretical investigation on the properties of manganese impurity centers in cubic boron and gallium nitrides. The calculations were performed using the all electron spin-polarized full-potential linearized augmented plane wave methodology. Our results indicate that manganese in boron nitride, in a neutral charge state, is energetically more favorable in a divacancy site as compared to a substitutional cation site. We present the results on stability, spin states, impurity magnetic moment, hyperfine parameters, and formation and transition energies of manganese at the divacancy site in several charge states.

Abstract: The electronic and structural properties of nickel-vacancy complexes in diamond were investigated by a total energy ab initio methodology. These results are discussed in the context of the electrically active centers, commonly found in synthetic diamond.

Abstract: The electronic and structural properties of isolated 3d-transition metal impurities in 3C, 4H, and 2H silicon carbide have been investigated bytotal energy ab initio methods. The stability, spin states and transition energies of substitutional (Si sub-lattice) Cr, Mn, and Fe impurities in several charge states were computed. Our results are discussed in the context of available experimental data.