Excited state structural analysis (ESSA) for correlated states of spin-flip type: application to electronic excitations in nanodiamonds with defects

Abstract

The previously developed ESSA for configuration interaction singles (CIS) method is extended to a more rigorous many-body theory of excited states based on spin-flip (SF) transformations. The so-called SF-CIS (SF approach for CIS) is used, and the respective ESSA indices are constructed. These are atomic excitation indexes L*A, interatomic charge-transfer numbers lA - > B, and others. By using these quantities, low-lying excitations in the modelled nanodiamonds with color centers (first of all, nitrogen-vacancy (NV) centers) are investigated at a semiempirical level of the theory. It is shown that the lowest excitations are significantly localized in a vicinity of the vacancy. Furthermore, the same excitations are characterized by a high interatomic charge transfer. All these features are common to both types of the NV centers (neutral NV0 and negative NV-).