The local vibrational modes of H in crystalline material were studied by means of infra-red absorption spectroscopy and uniaxial stress measurements. The H isotopes were introduced by proton or deuteron implantation. A predominant trigonal defect was identified which involved a pair of inequivalent H atoms, with local modes at 765, 1499, 1774 and 1989/cm. The structure and local modes of the H2* defect were calculated by using  ab initio  local density functional cluster theory. It was found that the structure was consistent with uniaxial stress experiments. The calculated frequencies were in reasonable agreement, and the isotope shifts were in good agreement, with the observed values.

M.Budde, B.B.Nielsen, R.Jones, S.Oberg, J.Goss: Materials Science Forum, 1995, 196-201, 879-84