Electron paramagnetic resonance and optical data on some basic Ni-related defects were compared, in conjunction with little considered information concerning the effects of spin–orbit coupling and the magnitude of the crystal field. New models were proposed for the electron paramagnetic resonance defects which were found in synthetic diamond grown at high pressures and high temperatures, with getters being used in order to reduce the content of N impurity. The defects included NIRIM-1 and NIRIM-2, which had sometimes been attributed to isolated interstitial Ni at an undistorted and distorted Td site, respectively. It was suggested that NIRIM-1 was more likely to be substitutional Nis+, 3d5, at a Td site, than the previously suggested: interstitial Nii+, 3d9. The NIRIM-2 was Nii+, 3d9, pinned at a site which was 0.308nm along <111> from a Bs- impurity; beyond one of its nearest C neighbors. This supported the suggestion that isolated interstitial Nii was mobile.

Do Isolated Interstitial Nickel Atoms Occur in Diamond? A Re-Examination of the Electron Paramagnetic Resonance Defects NIRIM-1 and NIRIM-2. J.M.Baker: Journal of Physics - Condensed Matter, 2003, 15[39], S2929-40