Potential energy surfaces for the lowest excited states of the nitrogen-vacancy point defects in diamonds: A quantum chemical study

Quantum chemical calculations of geometry relaxation in lowest excited states of neutral (NV0) and negatively charged (NV−) nitrogen-vacancy point defects in diamond have been performed employing the CASSCF method with a finite NC19H28 model cluster. Vibrations activated by the electronic transitions are determined by comparing calculated atomic displacements in the excited states with normal mode vectors, and the activated frequencies are evaluated as ∼600 cm−1. The barrier for N migration through the vacancy in NV− is estimated at the TD-B3LYP level and no significant decrease of this barrier (∼5 eV in the ground state) is found due to electronic excitations.