Phonon frequencies in beryllium along the principal symmetry directions have been determined by means of the slow neutron inelastic scattering technique. The data are analysed in terms of a six-neighbour force constant model and the force constants are evaluated. It is concluded that strong tensor forces are present in beryllium and the importance of this finding to basic theories of lattice dynamics is pointed out.

Detailed Raman scattering investigation of LiKSO₄ in phases II and III across the transition temperatureT_c ≃ 700 K is reported. Abrupt change in frequency and line width of the external and internal modes have been observed. Analysis of the results suggests lithium positional disorder and sulphate orientational disorder in the high temperature phase (II). The results also throw some light on the existence of twin domains in the crystal.

We have measured the kinetics of phase transition in LiKSO₄ (C₆⁶→C_3v⁴;T_c∼201 K) by monitoring the time-dependent change in Raman intensity of selected vibrational lines at various temperatures in the transformed phaseC_3v⁴. We find that the observed growth curves for several temperatures display a nearly universal shape when plotted against a suitably scaled time parameter. We interpret our results in terms of a phenomenological model of nucleation and growth.

Raman scattering investigation of phase transition in the ferroelectric Ba_0.95Ca_0.05TiO₃ is reported. The results suggest onset of significant dynamic disorder at 105°C. This corroborates findings of recent structural study regarding large positional disorder associated with Ti and O1 atoms well below the tetragonal to cubic transition temperature (∼150°C).