ORIENTATIONAL GLASS-TRANSITION IN (KBR)1-X(KCN)X QUADRUPOLAR GLASSES - A RAMAN-SCATTERING STUDY

Using Raman scattering experiments we have investigated the orientational glass transition in (KBr)i_x(KCN)x mixed crystals with concentrations a = 0.10, 0.25 and 0.50. The dynamical rotational disorder in the plastic phase results in strong dispersion effects in the cyanide libration mode observed in the low-frequency spectral region, around v = 50 cm-1. The freezing of the orientational degrees of freedom clearly shows up in a decrease of the libration width. At high frequency, v = 2076 cm-1, the inhomogeneous broadening of the CN" stretching vibration reflects increasing random strain fields consecutive to the orientational glass transition. © 1990 IOP Publishing Ltd.