Vibrations of Glasslike Disordered Systems. II. The A2B3 Network in Two Dimensions—Application to Vitreous As2Se3 and As2S3

A computer-generated two-dimensional A2B3 glasslike disordered network having a Gaussian distribution of A–B–A bond angles has been formulated as an approximate model of the vitreous layer-type chalcogenides As2Se3 and As2S3. A two-parameter potential function involving nearest-neighbor central and noncentral interactions has been used to generate the equations of motion which have been solved by application of the negative eigenvalue theorem. Under the appropriate choice of boundary conditions, the bands in the computed densities of states adequately reproduce those in the experimental spectra in number and position. Eigenvectors have been computed for selected frequencies throughout the spectra, and assignments of observed spectral bands to specific normal modes have been formulated.