Laser Raman study of single crystals of deuterated cadmium fluorosilicate

A laser Raman study of oriented single crystals of CdSiF 6 :6D 2 O at room temperature as well as at 10 K in all the six polarization geometries has been made. Also a detailed temperature dependent Raman study from room temperature to 10 K in ( yy ) polarization in the region of internal vibrations and lattice modes has been made. Abrupt changes have been observed in frequency shift, line-width and intensity of some of the bands at about 235 K. Some doubly degenerate modes show splitting at the same temperature. From these observations a phase change at about 235 K is inferred for this salt. It has been suggested that when the system is cooled, the lattice contracts and the water molecules lose their reorientational freedom to some extent which might result in the distortion of the [Cd(OD 2 ) 6 ] 2+ octahedra triggering a phase transition.