A Multiconfigurational Study of Negatively Charged Nitrogen-Vacancy Center in Diamond

Point defects in wide bandgap semiconductors have been shown to be promising for quantum sensing and information applications. Discoveries of new point defects tailored for specific applications require quantitatively reliable predictions of electronic and magnetic properties of pointe defects. Many-electron characteristics of the defect states demand theories beyond single-electron approach. Taking advantage of the spatially localized nature of the defects, we apply multiconfigurational quantum-chemistry methods to a prototype point defect such as a negatively charged nitrogen-vacancy center in diamond. Our methodology takes into account electron correlation, spin-orbit coupling (SOC) and dipolar spin-spin coupling (SSC) within many-electron configurations without fitting parameters. We find the correct ordering of the singlet and triplet states and identify the many-electron configurations of the singlet states. We also compute excitation energies and zero-field splitting due to SOC and SSC, which agree with experiment. The numerical procedure we have developed is general, and so it can be applied to other point defects.