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

Chang-Sheng Zha; John S Tse; William A Bassett

doi:10.1063/1.4963320

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

J Chem Phys. 2016 Sep 28;145(12):124315. doi: 10.1063/1.4963320.

Authors

Chang-Sheng Zha¹, John S Tse², William A Bassett³

Affiliations

¹ Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. N.W., Washington, DC 20015, USA.
² Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B2, Canada.
³ Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA.

PMID: 27782667
DOI: 10.1063/1.4963320

Abstract

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 ∼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, ∼27, ∼44, ∼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.