In situ Raman Study of ОН-Perovskite MgSi(OH)₆ at High Р–Т Parameters (up to 14 GPa, 420°С)

In situ Raman spectroscopy in a diamond anvil cell (DAC) is used to study ОН-perovskite MgSi(OH)₆ under compression in water and carbonate fluids at high Р–Т parameters (up to 14 GPa, 420°С). The ОН-perovskite ↔ 10 Å phase + хН₂О transition is either partially reversible or irreversible when there is a deficit of water in the system. When ОН-perovskite is compressed in carbonate fluid, the reversible transition shifts slightly to higher pressures, testifying to the drop in the activity of water when carbonate is added in the system.