An investigation was made of the binding and diffusion pathways for atomichydrogen in diamond using the semi-empirical atom superposition and electron delocalization molecular orbital theory. The bond-centered site was found to be more stable than the tetrahedral and hexagonal interstitial sites due to the formation of a low-lying band-gap orbital which takes the promoted electron. A second hydrogen binds even more stably to the nearby anti-bonding site with additional stabilization of the now doubly occupied band gap orbital. The bond-centered hydrogen was predicted to migrate along the high-density (110) planes in the diamond lattice with an activation barrier of 1.9eV. A carbon atom vacancy was found to attract interstitial H which bind to dangling orbitals on the surrounding C atoms. These bond strengths decrease as up to a maximum of four H atoms enters the vacancy. A hydrogen atom in a vacancy was found to increase the activation energy for vacancy migration.

Hydrogen Binding and Diffusion in Diamond. Mehandru, S.P., Anderson, Alfred B.: Journal of Materials Research, 1992, 7[3], 689-95