The spin state of the neutral silicon vacancy in 3C-SiC

Recent theoretical studies show that the neutral silicon vacancy (V-Si) in cubic silicon carbide (3C-SiC) exhibits negligible Jahn-Teller distortion. This provides an opportunity to study the energy sequence of different multiplets in a vacancy with genuine T-d symmetry. Calculations using the local spin density approximation give a spin triplet as ground state. The determination of the true ground state requires, however, the incorporation of configuration interactions. Using multiconfigurational self-consistent field calculations we show that the ground state of the neutral V-Si(0) in 3C-SiC is a spin singlet. The calculated energy difference, similar to 0.1 eV, in favor of the singlet spin state would still allow the experimental observation of the triplet state at high temperature. (C) 1999 American Institute of Physics. [S0003-6951(99)04940-2].