J. Phys. Chem. 1983, 87, 4174-4179
4174
Cubic Ice in Naturet E. Whalley Division of Chemistty, National Research Council, Ottawa, Ontario K 1A OR9, Canada (Received: October 15, 1982)
Ice occurs widely on the earth and planets and outside the solar system, and some of it may be in the form of ice IC. The purpose of this paper is to review the occurrence of ice ICin nature, particularly as it can be directly detected. It seems likely that Scheiner’s halo, a rare halo at -28O from the sun or moon, which has been reported only six times since the first report in 1629, is caused by octahedral crystals of cubic ice in the upper atmosphere. A patch of light about 35O from the sun was observed in Paris in 1677, and it is probably caused by the intersection of a lateral arc of Scheiner’s halo with the tail of the parhelion of the 22O halo. If this is correct, it is the only report of an arc of the 28’ halo. Natural polycrystalline snow crystals frequently have their c axes at -70” to one another. Kobayashi and colleagues have suggested that they are formed from small octahedral crystals of cubic ice by growth of basal planes on the octahedral faces. There seems little doubt that cubic ice often forms in the upper atmosphere.
1. Introduction
Ice I is produced in large quantities on the earth, exists in enormous quantities in the solar system,l and has probably been detected in interstellar pace.^.^ Some of this ice is in the form of ice Ih,the familiar hexagonal form. There is, however, a closely related form known as ice IC,or cubic ice, which has the diamond structure. Both kinds are made of puckered hexagonal layers stacked on top of one another. In ice Ih, two layers occur in a repeating unit, and each layer can be considered derived from the other by a reflection in the plane of the layer. There is a sixfold screw axis, 63, passing through the centers of the rings and the complete symmetry is B 3 / m m c or @h.
Ice IC can be considered to be made of the same hexagonal layers. Three layers occur in the unit cell and they are related to one another by successive translations along the diameter of a hexagon by one-half the diameter. The resulting structure is the same as the diamond structure and is cubic, in space group Fd3m. The hexagonal layers are in the (111) and equivalent planes, and so they are perpendicular to the diagonal axis of the cube, or, equivalently, on the octahedral faces. Ice Ih has, of course, been known since the early days of man. Ice ICwas f i t made and recognized as a new kind by Dew& in 1905. He compressed ice at 193 K to 15 kbar and recovered it after removing the pressure. He reported that “during the gradual heating up from -80°, it became milk-white from some new crystalline arrangement”. During the 19308, several workers obtained diffraction patterns of ice IC,but did not recognize them as due to a new form. Kirchner5 in 1930 condensed ice ICon a celluloid film, but mistook it for camphor, as was first recognized by Koniga6 In 1935, Burton and Oliver7condensed water vapor onto a copper rod at low temperatures. Below 193 K, they obtained an X-ray diffraction pattern that indicated “a marked change” (from ice Ih) “in the regularity of the arrangement of the molecules”, and between 183and 163 K obtained diffraction patterns of ice IC. They were, therefore, the second workers to recognize ice ICas a new form and provided the second method of preparation, but did not further characterize it and did not, of course, relate it to Dewar’s4 form. Below 158 K, they obtained amorphous ice for the first time. The structure of Kirchner’s and Burton and Oliver’s phase was worked out by Konig6 in 1942 using eIectron diffraction of thin N.R.C. No. 20953. 0022-3654/83/ 2087-4174$01.50/0
films, and he also showed that the phase could be made by heating amorphous ice, so giving a third preparative method. In 1963, it was shown in our own laboratoriese10 that all the high-pressure phases of ice that could be recovered at zero pressure and 77 K, including ice IV, for which the data were not published,’O changed to ice IC when heated. Dewar’s new phase was, therefore, identified as ice ICalmost 50 years after it was first made. As far as we know, then, ice ICis always formed when a metastable solid or vapor phase of water is transformed into ice I below -200 K; except that the vapor transforms to amorphous ice at low temperatures, which itself transforms to ice ICon heating to -150 K. By analogy with this, it seemed likely” that the liquid would freeze to ice ICinstead of to ice Ih at a low enough temperature. This prediction has recently been at least partly confirmed by Elarby et al.,12who have observed that solutions of 10.5 mol % lithium chloride in deuterium oxide, quenched to below the glass transition, crystallize by homogeneous nucleation to ice ICwhen warmed to between the glass transition temperature of 141 K and 161 K. Perhaps, then, small drops of water in the upper atmosphere may1’ sometimes freeze to cubic ice. Ice ICappears to be always metastable relative to ice Ih. It certainly transformed spontaneously to ice Ih at 153 Ks in 2-3 days at a rate that gave an amount that was just detectable by X-ray powder diffraction. If it is metastable, heat must be evolved at the transformation to ice Ih at constant pressure. Two independent measurements13J4 (1)C. B. Pilcher, S.T. Ridgway, and T. B. McCord, Science, 178, 1087-9(1972). (2) T. Owen in ‘‘Physics and Chemistry of Ice”,E. M e y , S. J. Jones, and L. W. Gold, Ed., Royal Society of Canada, Ottawa, 1973,pp 117-26. (3)E. F. Erickson, R. F. Knacke, A. T. Tokunaga, and M. R. Haas, Astrophys. J., 245, 148-53 (1981). (4)J. Dewar, Chem. News, 91, 216 (1905). (5)F. Kirchner, Phys. Z., 31, 772-3 (1930). (6)H.Konig, 2.Kristallogr., 105, 279-86 (1943). London, Ser. A , 153, (7)E. F.Burton and W. F. Oliver, Proc. R. SOC. 166-72 (1935). (8)J. E. Bertie, L. D. Calvert, and E. Whallev. J. Chem. Phvs.. 38. 840-6 (1963). (9)J. E. Bertie, L. D. Calvert. and E. Whallev. Can. J. Chem.., 42., 1373-8 (1964). (10) H. Engelhardt, L. D. Calvert, and E. Whalley, unpublished data. (11)E. Whalley, Science, 211, 389-90 (1981). (12)A. Elarby, J. F. Jal, J. Dupuy, P. Chieux, A. Wright, and R. Parriens, J.Phys. Lett., 43, L355-63 (1982). (13)J. A. McMillan and S. C. Los, Nature (London), 206, 806-7 (1965). (14)M.Sugisaki, H.Suga, and S. Seki, Bull. Chem. SOC.Jpn. 41, 2591-9 (1968).
Published 1983 by the American Chemical Society
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Cubic Ice in Nature
Flgure 1. Sketch showing how a hexagonal crystal of ice Ih refracts light at the angle of minimum deviation to form the 22' halo.
yielded about 155 J mol-l, but Ghormley15pointed out that much of this heat is caused by the release of surface energy when small ice ICcrystals, a few hundred angstroms across, transform to larger crystals of IC,and the difference of energy between ice Ih and ICmay be
