Ab initio supercell calculations on nitrogen-vacancy center in diamond: Electronic structure and hyperfine tensors

The nitrogen-vacancy center in diamond is a promising candidate for realizing the spin qubits concept in quantum information. Even though this defect has been known for a long time, its electronic structure and other properties have not yet been explored in detail. We study the properties of the nitrogen-vacancy center in diamond through density functional theory within the local spin density approximation by using supercell calculations. While this theory is strictly applicable for ground state properties, we are able to give an estimate for the energy sequence of the excited states of this defect. We also calculate the hyperfine tensors in the ground state. The results clearly show that (i) the spin density and the appropriate hyperfine constants are spread along a plane and unevenly distributed around the core of the defect and (ii) the measurable hyperfine constants can be found within about 7 A from the vacancy site. These results have important implications on the decoherence of the electron spin which is crucial in realizing the spin qubits in diamond.