Brillouin-scattering study of the liquid-glass transition inCaKNO3: Mode-coupling analysis

Polarized and depolarized Brillouin scattering from 0.4 Ca(${\mathrm{NO}}_3$ ${)}_2$-0.${6\mathrm{K}\mathrm{N}\mathrm{O}}_3$ was investigated in the temperature range of 320 to 640 K using a six-pass Sandercock tandem Fabry-Perot interferometer. The polarized spectra were analyzed with a simplified version of mode-coupling theory, in which the small-q density fluctuation modes probed by light scattering couple only to pairs of modes at ${\mathit{q}}_0$ corresponding to the first peak in the structure factor S(q). The density correlation function φ(${\mathit{q}}_0$,t) determined by neutron spin-echo experiments by Mezei et al. was used as input in the analysis, producing excellent fits to the experimental data. The depolarized spectra were analyzed with a phenomenological viscoelastic model including ${\mathrm{NO}}_3^{\mathrm{-}}$ orientational relaxation.