Neutron inelastic scattering study of Se-As-Ge glasses: A test of the vibrational isocoordinate rule

Determinations of the generalized neutron vibrational density of states (GVDOS) made on samples of Se-As-Ge glass alloys by neutron inelastic scattering at the NIST Center for Neutron Research are presented. It is observed that up to a certain characteristic vibrational energy the GVDOS are nearly identical for alloys over a broad range of compositions as long as they have the same average coordination number [r]. In the present work this feature, referred to as the vibrational isocoordinate rule (VIR), is established for samples of Se-As-Ge alloys over the entire glass-forming region with [r] ranging from 2.16 through the theoretical rigidity percolation threshold 2.4 up to 3.2. Compositional exceptions to the VIR have been found along and near the Se-As binary alloy line above [r] = 2.4. [S0163-1829(99)12105-2].