The properties of transition metal-N complexes were examined by using ab initio density functional theory. Attention was focused on 2 classes of NiN complex. One was the low-symmetry semi-vacancy NEn center, and the other was the higher-symmetry ABn center. The former was examined with regard to its stability and electronic structure. It was found that the stability of the various NEn isomers confirmed theories concerning their formation. The electronic structure of the centers was not as simple as previously believed, and it was suggested that the vacancy model was to be preferred over the Ludwig-Woodbury model. The new ABn centers were also stable. Their electronic behavior was more usual, and largely supported the Ludwig–Woodbury scheme.

Properties of Nickel Nitrogen Complexes in Diamond - Stability and Electronic Structure. K.Johnston, A.Mainwood: Diamond and Related Materials, 2003, 12[3-7], 516-20