An investigation was made of  vibrational properties and lattice distortion of negatively charged nitrogen-vacancy (NV-) center in diamond. Using the first-principles electronic structure calculations, it was shown that the presence of NV- center leads to appearance of a large number of quasilocalized vibrational modes (qLVMs) with different degrees of localization. The vibration patterns and the symmetries of the qLVMs were presented and analyzed in detail for both ground and excited orbital states of the NV- center. It was found that in the high-symmetry (C3v) excited orbital state a pair of degenerate qLVMs becomes unstable, i.e., has formally negative frequencies, and the stable excited state has lower (C1h) symmetry. This was a direct indication of the Jahn-Teller effect, and the studies suggested that the dynamical Jahn-Teller effect in the weak-coupling regime takes place. A detailed comparison was also made of the present results and available experimental data on the vibrations involved in optical emission/absorption of the NV- centers. It was directly demonstrated that, among other modes, the qLVMs crucially affected the optical properties of the NV- centers in diamond, and identified the most important groups of qLVMs. These results were important to a deeper understanding of the optical properties and the orbital relaxation associated with lattice vibrations of the NV- centers.

Vibrational Modes and Lattice Distortion of a Nitrogen-Vacancy Center in Diamond from First-Principles Calculations. J.Zhang, C.Z.Wang, Z.Z.Zhu, V.V.Dobrovitski: Physical Review B, 2011, 84[3], 035211