The NV0 defects in diamond: A quantum mechanical characterization through its vibrational and Electron Paramagnetic Resonance spectroscopies

The NV0 defect in diamond has been investigated quantum-mechanically, by analyzing its structural, electronic, vibrational and magnetic properties. The possible spin states for NV0 are a quartet NVq0 (4A2 symmetry) and a doublet (2E symmetry). In the latter state a single electron occupies a double degenerate level producing a Jahn Teller distortion that removes the degeneracy and lowers the total energy. The symmetry reduces from C3v to CS and two local minima are indeed identified, to be indicated as NVd10 (2A′ symmetry) and NVd20 (2A″ symmetry). NVd10 is the ground state, and is more stable than NVq0 by ~ 0.5 eV, and than NVd20 by ~ 0.2 eV, irrespective of the functional or basis set adopted. The EPR hyperfine coupling tensor has been computed for NVq0 and has been found to be in excellent agreement with available experimental data. The IR spectra of the NV defects (the three neutral cases and also the negatively charged one, for comparison) show specific peaks and shape that characterize each system and differentiate the spectra according to the spin and charge state. The Raman spectra of the NV0 defects shows a single peak, redshifted with respect to the single peak of pristine diamond by 2 cm−1 only, but in turn well separated from the negatively charged form of the defect.