The vacancy-nitrogen-hydrogen complex in diamond: a potential deep centre in chemical vapour deposited material

Following recent experiments leading to the assignment of a trigonal vacancy-nitrogen-hydrogen complex in single-crystal chemical vapour deposited diamond, we have employed first-principles density functional supercell and cluster techniques to examine the structure and properties of such a defect. We find that the trigonal defect where H bonds directly to the nitrogen atom is unstable and instead a planar structure with H bonding to carbon is the ground state. The complex is expected to be thermally stable as well as optically, magnetically and electrically active. We also discuss the dynamic properties of the complex, and tentatively propose a trigonal form of the defect made up from a superposition of the three equivalent C_1h configurations.