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Updated: Aug 17, 2026

Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 7, 2013
New transformations of CO(2) at high pressures and temperatures
O Tschauner1, H K Mao, R J Hemley
1Geophysical Laboratory and Center for High-Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington, D.C. 20015, USA.
Abstract:
CO(2) laser heating of solid CO(2) at pressures between 30 and 80 GPa shows that this compound breaks down to oxygen and diamond along a boundary having a negative P-T slope. This decomposition occurs at temperatures much lower than predicted in theory or inferred from previous experiment. Raman spectroscopy and x-ray diffraction were used as structural probes. At pressures higher than 40 GPa the decomposition is preceded by the formation of a new CO(2) phase (CO(2)-VI). These findings limit the stability of nonmolecular CO(2) phases to moderate temperatures and provide a new topology of the CO(2) phase diagram.
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