Network dynamics of chalcogenide glasses. I. Germanium diselenide

The scattering function S(Q,E) of vitreous GeSe₂ at 13 K was measured with inelastic neutron scattering over a wide range of variables (1<Q<8 A^-1, 0<E<45 meV), with use of a chopper spectrometer at the Intense Pulsed Neutron Source. The data are analyzed in terms of the effective one-phonon density of states G(E), the Q dependence of S(Q,E) at different values of energy transfer E, and the elastic structure factor Sel(Q). The data are discussed in terms of the normal modes of vibration of a Ge(Se1/2{)}₄$ molecule. Certain features in the data can be unambiguously identified with such modes on the basis of the behavior of the dynamic structure factor S(Q,E) at fixed E. Other features cannot be explained in this way and their understanding must await the development of a detailed microscopic model.