Thermodynamic stability of hexagonal and cubic ices

Tanaka, Hideki; Okabe, Ichiro

doi:10.1016/0009-2614(96)00824-x

Cited by 21 publications

(18 citation statements)

References 14 publications

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“…The thermodynamically stable form of ice at ambient temperature and pressure is ice Ih, which has a hexagonal crystal structure [6] . Hexagonal prism growth is the basic growth morphology of ice Ih, and the growth of simple ice prisms has therefore undergone much investigation [7] .…”

Section: Introductionmentioning

confidence: 99%

Surface Transition on Ice Induced by the Formation of a Grain Boundary

2011

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Interfaces between individual ice crystals, usually referred to as grain boundaries, play an important part in many processes in nature. Grain boundary properties are, for example, governing the sintering processes in snow and ice which transform a snowpack into a glacier. In the case of snow sintering, it has been assumed that there are no variations in surface roughness and surface melting, when considering the ice-air interface of an individual crystal. In contrast to that assumption, the present work suggests that there is an increased probability of molecular surface disorder in the vicinity of a grain boundary. The conclusion is based on the first detailed visualization of the formation of an ice grain boundary. The visualization is enabled by studying ice crystals growing into contact, at temperatures between −20°C and −15°C and pressures of 1–2 Torr, using Environmental Scanning Electron Microscopy. It is observed that the formation of a grain boundary induces a surface transition on the facets in contact. The transition does not propagate across facet edges. The surface transition is interpreted as the spreading of crystal dislocations away from the grain boundary. The observation constitutes a qualitatively new finding, and can potentially increase the understanding of specific processes in nature where ice grain boundaries are involved.

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Section: Introductionmentioning

confidence: 99%

Surface Transition on Ice Induced by the Formation of a Grain Boundary

2011

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“…Under the assumption that the entropy difference S sd→h is close to zero (e.g., Tanaka, 1998;Tanaka and Okabe, 1996), G sd→h equals H sd→h . The transformation of ice I sd to ice I h at temperatures above 180 K has been studied extensively with differential scanning calorimetry (DSC; e.g., Handa et al, 1986;Mayer and Hallbrucker, 1987;McMillan and Los, 1965;Sugisaki et al, 1968).…”

Section: Comparison To Literature Datamentioning

confidence: 99%

The vapor pressure over nano-crystalline ice

2018

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Abstract. The crystallization of amorphous solid water (ASW) is known to form nano-crystalline ice. The influence of the nanoscale crystallite size on physical properties like the vapor pressure is relevant for processes in which the crystallization of amorphous ices occurs, e.g., in interstellar ices or cold ice cloud formation in planetary atmospheres, but up to now is not well understood. Here, we present laboratory measurements on the saturation vapor pressure over ice crystallized from ASW between 135 and 190 K. Below 160 K, where the crystallization of ASW is known to form nano-crystalline ice, we obtain a saturation vapor pressure that is 100 to 200 % higher compared to stable hexagonal ice. This elevated vapor pressure is in striking contrast to the vapor pressure of stacking disordered ice which is expected to be the prevailing ice polymorph at these temperatures with a vapor pressure at most 18 % higher than that of hexagonal ice. This apparent discrepancy can be reconciled by assuming that nanoscale crystallites form in the crystallization process of ASW. The high curvature of the nano-crystallites results in a vapor pressure increase that can be described by the Kelvin equation. Our measurements are consistent with the assumption that ASW is the first solid form of ice deposited from the vapor phase at temperatures up to 160 K. Nano-crystalline ice with a mean diameter between 7 and 19 nm forms thereafter by crystallization within the ASW matrix. The estimated crystal sizes are in agreement with reported crystal size measurements and remain stable for hours below 160 K. Thus, this ice polymorph may be regarded as an independent phase for many atmospheric processes below 160 K and we parameterize its vapor pressure using a constant Gibbs free energy difference of (982 ± 182) J mol −1 relative to hexagonal ice.

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“…The system consists of a fixed number (N) of water molecules (N 192). The water molecules interact with each other via the TIP4P potential [4][5][6] and with the walls via the 9-3 Lennard-Jones potential [7]. The long-range waterwater intermolecular potential is smoothly truncated at 8.7 Å.…”

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confidence: 99%