Ultrahigh pressure phase transition in ice
Israel Osmond1, Mikhail A Kuzovnikov1, David A Lewis1,2
1Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh, UK.
Abstract:
One of the most enduring problems in dense H2O ice has been the experimental realization of the pressure-induced symmetry breaking of cubic ice X to an orthorhombic crystal structure. Here, through diamond anvil cell experiments combined with synchrotron X-ray diffraction and Raman spectroscopy techniques, we demonstrate that post-symmetrization, the crystal structure of ice X continuously distorts with pressure. Subjecting ice to pressures in excess of 308(5) GPa, we observe a first-order phase transition to ice XXII, consistent with the long-predicted phase possessing an orthorhombic crystal structure with Pbcm symmetry. We find that ice XXII is stable to pressures of at least 340(5) GPa.
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