The elastic anomaly of KCN at 168 K

Abstract

The Brillouin linewidths of longitudinal phonons (qllell[1, 0, 0]) and soft transverse phonons (q//[1, 1, 0] ; e//[0, 0, 1]) have been measured for the first time in KCN in its cubic phase above the elastic phase transition temperature. We propose a semi phenomenological model which explains the temperature variation of both these linewidths and of the related elastic constants, and, in particular, the absence of any spectacular variation of the transverse phonon linewidth close to the transition in spite of the soft character of the related elastic constant