The incorporation of H2 molecules at interstitial sites in various semiconductors was investigated by using a density-functional pseudopotential approach. It was found that the vibrational frequency of the interstitial molecules was shifted downwards as compared to those of the free molecule. The results confirmed the attribution of Raman lines to interstitial H2 in GaAs, but contradicted the suggestion that the frequency for H2 in Si was close to the free-molecule value. An appreciable weakening of the H-H bond was related to the semiconductor host charge density near to the interstitial site.

C.G.Van de Walle: Physical Review Letters, 1998, 80[10], 2177-80