Vibrational properties of metastable diatomic hydrogen complexes in crystalline silicon

The vibrational modes of a recently proposed diatomic hydrogen complex in Si are examined through ab initio pseudopotential calculations. The hydrogen atom occupying the bond-centered position of the complex is found to have a higher stretching frequency of 2070 ${\mathrm{cm}}^{\mathrm{-}1}$ as compared to 1480 ${\mathrm{cm}}^{\mathrm{-}1}$ for the antibonding-centered hydrogen atom. This frequency shift results from the different orbital hybridizations of the two central Si atoms of the complex.