Spin-polarized local density functional cluster calculations were performed for substitutional Ni and Ni-H2 complexes. It was found that Ni- underwent a Jahn-Teller distortion, along <100>, with Ni moving slightly along the cube axis. The distorted state gave b1, b2 and a1 levels, in ascending order of energy, within the gap; in agreement with experiment. Several possible Ni-H2 defects were investigated, and it was found that the lowest-energy structure consisted of a substitutional Ni atom; together with two H atoms at anti-bonding sites to two Si neighbors of Ni. This led to H-related vibrational modes and to a spin-polarized charge density which were close to those for Pt-H2.

R.Jones, S.Oberg, J.Goss, P.R.Briddon, A.Resende: Physical Review Letters, 1995, 75[14], 2734-7