Rings, intermediate-range order and vibrational spectra of chalcogenide glasses

Short-range order, intermediate-range order and vibrational density of states of vitreous GeSe2 are investigated using the molecular dynamics (MD) method. The static structure factor exhibits the first sharp diffraction peak (FSDP), a characteristic of intermediate-range order in chalcogenide glasses, as well as all the other peaks observed in structural measurements. The anomalous dependence of the FSDP, i.e. the decrease in its height on cooling is due to frustration enhanced by the increased density. The calculated phonon density of states in the glass shows peaks at 8.0, 10.8, 26.4, 34.4, and 37.2 meV, which are all in good agreement with neutron experiments. In addition a companion line, A1c, to the symmetric breathing mode A1 (26.4 meV) is identified with a feature at 27.8 meV. Raman studies also find A1c to be ∼1.5 meV higher than the A1 mode. Our calculations show that the A1c mode arises due to vibrations of tetrahedra belonging to 5- and 7-fold rings. © 1988.