The N-vacancy center, a paramagnetic defect in diamond, was investigated with regard to its electronic structure by applying ab initio density functional theory to 5 different N-vacancy center models of 2 different cluster sizes. The symmetry and energetics of the low-lying states were described, and the optical frequencies obtained were compared with experimental results. The major transition of the negatively charged N-vacancy centers was computed to within 25 to 100meV accuracy, and it was found that it was energetically favorable for substitutional N atoms to donate an electron to NV0. The excited state of the major transition and the NV0 state with a neutral donor N were found to be close in energy.

Electronic Structure of the Nitrogen-Vacancy Center in Diamond from First-Principles Theory. J.A.Larsson, P.Delaney: Physical Review B, 2008, 77[16], 165201 (8pp)