HIGH-PRESSURE X-RAY AND RAMAN-STUDY OF CESIUM THIOCYANATE

High pressure X-ray and Raman experiments have been conducted on cesium thiocyanate (CsSCN) using a diamond anvil cell. The pressure-volume relationship of CsSCN has been investigated using X-ray diffraction under quasi-hydrostatic conditions up to 108 kbar. The compression data were fitted to the Birch equation with B0 and B'0 taking values of 73 kbar and 20. With B'0 set at 2, 4, 6 and 8 bulk modulus values of 277, 214, 173 and 145 kbar were obtained. The data were also fitted to the Murnaghan equation with B0, B′0 and B″0 taking values of 138 kbar, 5.2 and 0.096 kbar-1. The Raman spectrum of CsSCN was observed up to 80 kbar, also under quasi-hydrostatic conditions. Only external modes were investigated. Two high pressure phase transitions are seen in the regions 10-33 and 54-62 kbar, the first concurring with the result of Actams and Pogson (J. Raman Spectrosc. 19, 321, 1988). The transitions are characterized by changes in the gradients of the mode frequency-pressure plots. No mode softening is observed. © 1990.