Neutron scattering studies of glassy and liquid ZnCl2

Neutron scattering measurements on ZnCl2 have been performed with both the DUALSPEC high-resolution powder diffractometer and triple-axis spectrometer at Chalk River Laboratories. The static structure factor S(Q) and the elastic structure factor S(Q, 0) are compared at temperatures between 300 and 680 K, spanning the glass, supercooled liquid and normal liquid phases. The temperature dependence of S(Q, 0) is more pronounced than that of S(Q), showing that there is a large inelastic component in S(Q). The heights of the peaks in S(Q, 0) and S(Q) exhibit a change in slope with temperature at T-g = 375 +/- 5 K, the glass transition temperature. The faster decrease observed above T-g is caused by the onset of beta-relaxation, as predicted by mode-coupling theory. (C) 1998 Elsevier Science B.V. All rights reserved.