VIBRATIONAL SPECTROSCOPY AT HIGH-PRESSURES .59. AN INFRARED AND RAMAN-STUDY OF LITHIUM HYDROXIDE MONOHYDRATE - HYDROGEN-BOND FORMATION AT HIGH-PRESSURES

Changes in the infrared and Raman spectra of lithium hydroxide monohydrate indicate that a phase transition occurs at close to 90 kbar upon compression. In particular, there is a doubling of the vibrations associated with the hydroxyl ion and a change in sign of the dv/dp values for the hydroxyl O-H stretches from positive to negative. These results indicate that the transition involves the formation of weak hydrogen bonds, in which the hydroxyl hydrogens taken part, and the doubling of the size of the primitive unit cell. A large hysteresis was observed with the reverse transition occurring near 33 kbar.