A new metastable diatomic H complex was suggested for crystalline material. Some  ab initio  calculations showed that the complex was about 1.2eV more stable than were 2 separated neutral H atoms in their most energetically favorable configurations. A new diffusion mechanism was proposed which was based upon metastable and molecular H-complex formation and dissociation.

K.J.Chang, D.J.Chadi: Physical Review Letters, 1989, 62[8], 937-40