Relation of the Si-H stretching frequency to the nanostructural Si-H bulk environment

We propose a model which describes the frequency shift (Delta omega(SM)) of the stretching mode (SM) of Si - H monohydrides (MH's) when incorporated in hydrogenated amorphous silicon (a-Si:H) with respect to the unscreened MH SM at similar to 2099 +/- 2 cm(-1). The model is based on an effective medium approximation of the dielectric using multiple Lorentz-Lorenz dielectrics, corresponding to a host dielectric with MH's embedded in cavities, separately. The Delta omega(SM) as derived in this model correctly predicts all bulk MH-SM positions in a-Si:H films and relates it directly to the nanostructure of the MH bulk configurations.