New Raman measurements for H2O ice VII in the range of 300 cm(-1) to 4000 cm(-1) at pressures up to 120 GPa

摘要

Raman spectroscopic measurements for H2O ice VII have been conducted to 120 GPa at 300 K in the spectroscopic range of 300-4000 cm(-1). Both moissanite and diamond anvils were used for the experiments. This overcomes the problems of overlapping spectra between the diamond anvil and sample, which had prevented the observation of the stretching modes at pressures higher than similar to 23 GPa in all previous measurements. The new results reveal many bands which have not been reported before. The pressure dependences of the Raman modes show anomalous changes at 13-15, similar to 27, similar to 44, similar to 60, and 90 GPa, implying possible structural changes at these pressures. The new results demonstrate that the predicted symmetric hydrogen bond phase X transition does not occur below 120 GPa. Published by AIP Publishing.