Neutron Scattering Study of the Dynamics of(KCN)0.5(KBr)0.5

Our earlier measurements on pure KCN and ${\mathrm{}\left(\mathrm{KCN}\right)\mathrm{}}_{0.25}$ ${\mathrm{}\left(\mathrm{KBr}\right)\mathrm{}}_{0.75}$ have been extended to mixed crystals of ${\mathrm{}\left(\mathrm{KCN}\right)\mathrm{}}_{0.5}$ ${\mathrm{}\left(\mathrm{KBr}\right)\mathrm{}}_{0.5}$. From a comparison of the observed neutron scattering line shapes to those predicted by a simple extension of the theory used to describe pure KCN, it is concluded that this theory does not describe the mixed systems correctly. This Letter suggests that the current results may be indicative of the formation of a "glass" phase at low temperatures in these mixed systems.