In situ observations of a high-pressure phase of H2O ice

• Published in: Science (American Association for the Advancement of Science) Vol. 281; no. 5378; pp. 809 - 812
• Main Authors: CHOU, I.-M, BLANK, J. G, GONCHAROV, A. F, MAO, H.-K, HEMLEY, R. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 07.08.1998; The American Association for the Advancement of Science
• Subjects: Climate; Crystalline rocks; Earth sciences; Earth, ocean, space; Evidence; Exact sciences and technology; Experimental petrology; Geology; Grade Point Average; High pressure research; Hydrology; Hydrology. Hydrogeology; Ice; Ice crystals; Least Squares Statistics; Phase diagrams; Scientific Concepts; Water; morphology; phase diagrams; anisotropy; melting; ice; crystal form; Raman spectroscopy; high pressure; bulk density; P-T conditions; growth; diamond anvil cells; stability
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.281.5378.809

A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10 degrees and 50 degreesC. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.