The nitrogen-vacancy (NV) center is a paramagnetic defect in diamond with applications as a qubit. Here, we investigate its electronic structure by using ab initio density functional theory for five different NV center models of two different cluster sizes. We describe the symmetry and energetics of the low-lying states and compare the optical frequencies obtained to experimental results. We compute the major transition of the negatively charged NV centers to within 25–100 meV accuracy and find that it is energetically favorable for substitutional nitrogens to donate an electron to ${\text{NV}}^0$. The excited state of the major transition and the ${\text{NV}}^0$ state with a neutral donor nitrogen are found to be close in energy.

• Received 31 July 2007

DOI:https://doi.org/10.1103/PhysRevB.77.165201