We have set up a simple model for the high frequency vibrational modes of AnXm glasses (i.e. those modes which are probed most easily in infrared absorption and Raman scattering experiments). This model involves using only nearest neighbor central forces and is a generalization of previous work by Sen and Thorpe for AX2 glasses in which the vibrational spectrum is derived from the connectivity matrix of the structure. Simple algebraic expressions are obtained for the band edges and applied to the spectra of glassy GeS2, GeO2 and P2O5. The dominant features of the spectra are associated with particular band edges in the central force model, taking due account of selection rules governing polarized Raman scattering in network glasses. Errors to be expected from the omission of non-central forces and long-range Coulomb forces are discussed.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry