HIGH-PRESSURE PHASE-TRANSITIONS IN LI2SO4

Raman spectroscopy of Li2SO4 was performed for pressures in the range 1 bar to 80 kbar. The crystal remains in the original phase if the pressure is kept below 13 kbar. At this pressure the spectrum undergoes qualitative changes in a continuous way as a function of time, up to about eight hours. This was interpreted as a dynamical transition to a new structure, called the phase. Substantial modifications in the spectra were also observed to occur when the pressure exceeded 35 kbar. Above this value the results suggest another high-pressure phase with a noncentrosymmetric space group. © 1990 The American Physical Society.