High-Pressure Single-Crystal Studies of Ice VI

By means of a precession camera incorporating a diamond-anvil high-pressure cell, x-ray diffraction data can be obtained from single crystals of ice VI produced and maintained under high pressures. The cell constants for ice VI at room temperature and approximately 9 kilobars are: a = 8.38 angstrom, b = 6.17 angstrom, c = 8.90 angstrom. The unit cell is orthogonal and the space-group aspect is compatible with P^{* *}a. These data for single crystals agree with previously reported unindexed data obtained for polycrystalline ice VI, within the limits of experimental error. The single crystals of ice VI were grown in a diamond-anvil pressure cell, distilled water and a metal gasket being used.