Dynamics of modified glass networks

A comparative study of the atomic dynamics of a-Li2Si2O5 and pure SiO2 glas s was performed using neutron inelastic scattering and applying the isotope substitution technique to suppress the coherent scattering from the networ k modifying Li atoms. The generalized vibrational density of stares G (omeg a) determined in the full energy range up to 150 meV differs clearly in the high energy range and also at low energies. A strong broadening and a shif t to lower energies of the sharp lines in the spectrum of SiO2 is observed in the spectrum of the modified network glass. A detailed analysis of the m easured dynamic structure factor S(Q, omega) is used to determine the chang e of the SiO2 network force constants by the network modifier, which again is used to support a specific model of the modification in the Si-O network .