S.N. Yannopoulos, E.A. Pavlatou
Chimica Chronica-New Series (1994), 23, 257-263
Photon correlation and Brillouin spectroscopy have been applied in the glass forming systems ZnCl2, ZnBr2 and the 50% ZnCl2-ZnBr2 mixture, in order to study the dynamics of local density fluctuations below Tg and far above Tm. The density correlation function of pure ZnCl2 near Tg is well represend by the non-exponential form exp(-t/τ)β with β=0.706±0.012 insensitive to temperature. The high value of β parameter categorizes ZnCl2 in the class of relative "strong" glasses with an Arrhenius temperature dependence of relaxation time τ near Tg (Tg+80°C). The hypersonic properties of pure components and the 50% mixture were also studied in the GHz region, where a single relaxation process was revealed (β=1). The limiting sound velocities uo and u∞ were calculated, showing up a linear decrease with temperature. The longitudinal relaxation time τi was found to follow an Arrhenius type relation.