HIGH-PRESSURE RAMAN AND FTIR STUDIES OF SOLID POTASSIUM, RUBIDIUM ANDCESIUM HYDROXIDES

Effects of compression on the Raman and IR modes of KOH(D), RbOH(D) an d CsOH(D) have been measured at pressures up to 20 GPa and temperature s down to 100 K using the diamond anvil technique. For all three hydro xides an ordering transition into the respective hydrogen-bonded low-t emperature phases was found below 1 GPa at room temperature. In additi on, the spectra of KOH(D) and RbOH(D) show significant changes at pres sures above 6.5 GPa, which point to the existence of a new phase. The decrease in frequency of the IR- and Raman-acive O-H(D) strectching vi brations with increasing compression indicates that hydrogen bonds exi st also in the new high-pressure phase VI. The variation of the O-O di stance at the phase transition IV double-line arrow pointing right VI is estimated by using a double-minimum potential.