Partial vibrational density of states for amorphous solids from inelastic neutron scattering

We introduce coherent inelastic neutron scattering with isotope substitution as a technique for measuring site-specific information on the vibrational dynamics of amorphous solids. The technique is used to extract experimentally the partial vibrational density of states G(alpha) (E) for both Ge and Se in the prototypical network-forming glass GeSe2, where alpha specifies the chemical species and E denotes the energy. The efficacy of the approximations used in interpreting the experimental data is validated by using a first-principles model, for which the set of true partial vibrational density of states is directly accessible. Our approach offers an opportunity for exploring accurately the vibrational dynamics of disordered materials.