Ab initio modeling of the electronic and spin properties of the [NV]− centers in diamond nanocrystals

Abstract

The electronic and spin properties of different nanocrystals of carbon are studied. The properties of these cluster systems are modeled in terms of the ab initio (Hartree-Fock) and semiempirical (PM3, AM1) quantum-chemical methods. The calculations are performed for different carbon nanocluster systems: defect-free and with [NV]− centers, hydrogen passivated (C38H42, C71H84, C86H78), and with a free (unpassivated) surface (C38, C71, C86). The spin properties of unhydrated nanoclusters were studied for the first time. The structure of all the clusters under study was optimized using the total energy minimization principle. It is shown that, in the case of hydrated carbon nanocrystals passivated by hydrogen atoms, diamond-like clusters are formed. The atomic structure of an unpassivated nanocrystal depends on the number of atoms in the cluster, as well as on its initial geometrical parameters. In some cases, clusters with a fullerene-like surface are formed. In hydrogenpassivated diamond nanocrystals with [NV]− centers, the spin density is localized at the nuclei of C atoms nearest to the center vacancies. For the unpassivated counterparts, the spin density is localized at the nuclei of C atoms forming the surface of the corresponding nanocrystal.