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

Recent theoretical studies show that the neutral silicon vacancy ${\mathrm{(V}}_{\mathrm{Si}})$ 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 $V_{\mathrm{Si}}^0$ in 3C–SiC is a spin singlet. The calculated energy difference, $\text{∼0.1\hspace{0.05em}}\mathrm{eV},$ in favor of the singlet spin state would still allow the experimental observation of the triplet state at high temperature.