Interpretation of Experimentally Determined Growth Rates of Ice Crystals in Supercooled Water

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Abstract
The results of recent measurements of the growth rate of dendritic ice single crystals along the basal plane in supercooled water are presented. These results are discussed in the light of the theory of Bolling and Tiller for a heat-flow controlled-growth mechanism and in the light of the molecular kinetic theory developed by Cahn. It was found that the growth rate of ice dendrites in supercooled water cannot completely be understood on the basis of a heat-flow controlled-growth mechanism but has to be explained on the basis of the combined mechanisms of heat dissipation and molecular-growth kinetics. Our analysis of the growth kinetics showed that at bath supercoolings between 0° and 9°C the growth rate of ice dendrites varied with the square of the interface supercooling in accordance with a growth mechanism which involves the advance of a diffuse interface by a lateral motion of steps originating at screw dislocations. At bath supercoolings larger than 9°C the growth rate varied linearally with the interface supercooling in accordance with a continuous-growth mechanism by which the surface advances normal to itself without the need of steps. The deviations from this behavior made evident by some of the experimental results are explained in terms of a reduction of the growth rate of individual ice dendrites as a consequence of their thermal interaction.

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