Using a generalized Hubbard Hamiltonian, many-electron calculations of energy levels and corresponding wave functions of negatively charged and neutral nitrogen-vacancy centers in diamond were reported. The energies, orbital, and spin symmetries of the ground and excited states were in good quantitative agreement with available optical and electron paramagnetic resonance measurements. The many-electron wave functions were employed to predict the spin density on the N and C atoms in the ground and excited states. The present model explained the recent, experimentally observed definite nonzero spin density on N atom for the 4A2 excited state of the neutral charge state of NV (NV0) based on the multiple electronic configuration of the corresponding many-electron wave function

Many-Electron States of Nitrogen-Vacancy Centers in Diamond and Spin Density Calculations. A.Ranjbar, M.Babamoradi, M.H.Saani, M.A.Vesaghi, K.Esfarjani, Y.Kawazoe: Physical Review B, 2011, 84[16], 165212