Simultaneous Measurements of Sound Velocity and X-ray Diffraction of Ice VII to 19 GPa and 873 K
Abstract
We have measured the sound velocity of Ice VII by Brillouin spectroscopy using membrane-style diamond anvil cell with an external Mo-wire resistance heater at elevated temperatures to 873 K at pressures of 2 GPa to 19 GPa. The unit cells of Ice VII and Au were determined by synchrotron X-ray diffraction, using Au as an in situ pressure gauge. All our samples contained were contained within and chemically insulated from the Re-gasket hole by a gold liner. We determined the melting of Ice VII by monitoring the sound velocity drop and the disappearance of diffraction pattern of Ice VII upon melting. Below ~8 GPa, our results are consistent with the previously determined melting curves (Datchi et al. 2000; Frank et al. 2004; Lin et al. 2004; Goncharov et al. 2005). However, our determination of the melting temperature at 12.5 GPa results in a discrepancy of at least 130 K. Given the care taken in the present experiments to avoid potential contamination of the water sample due to reactions at high temperatures between the sample and the gaskets and/or pressure gauges, our new measurements likely provide the first measurements on pure water which displaies an extended stability field of the solid phase. Thus, our new measurements suggest that the melting curve of H2O at high pressure needs to be reevaluated.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMMR31B..02S
- Keywords:
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- 5422 PLANETARY SCIENCES: SOLID SURFACE PLANETS / Ices