Shape Instability of Crystals of Ice, Carbon Dioxide and Ammonia Grown in a Cold Chamber

[摘要] According to Mullins and Sekerka's perturbation method, shape instability of ice crystals growing in a cold chamber was calculated under more general and more proper conditions for ice crystal growth in a vapor phase. The sublimation coefficient was taken into consideration.Result of the calculation was compared with experimental results on shapes of small ice crystals (the order of the size was tens of microns or less) in air under low pressure, small ice crystals in the atmospheres of hydrogen, carbon dioxide and argon-helium mixture. Shapes of carbon dioxide crystals and ammonia crystals were also compared with the calculation.It has been pointed that difference between shapes of ice crystals grown in various atmospheres is mainly attributable to difference in the diffusion coefficients of water vapor under conditions of small value of the sublimation coefficient, and partly attributable to difference in the thermal conductivities of the gases. Difference between shapes of crystals of ice, carbon dioxide, and ammonia is probably attributable to difference in degree of supersaturation and surface tensions.

[学科分类] 大气科学