Anisotropic Growth Kinetics and Pattern Formation of Ice

与匹兹堡卡内基-梅隆大学的研究人员合作，研究了具有多面冰晶的图案形成机制。首先，利用Mach-Zehnde干涉仪原位观察了单向生长过程中冰晶界面的图案形成。利用干涉条纹分析杂质扩散场，首次给出了在界面前发生本构过冷的直接证据。Mullins-Sekerka不稳定性理论基本上是一种线性稳态理论，也适用于冰界面的模式形成。其次，在冰晶生长实验结果的基础上，建立了冰在过冷水中冰盘生长的新模型。结果表明，根据基面生长动力学的不同，在过冷水中存在两种不同的冰晶过程模式（即螺旋生长或基面二维成核生长）。这一结果为认识多面晶体的图案形成提供了新的前景。第三，分子动力学模拟。也对冰面和冰水界面进行了研究。在分子水平上精确地讨论了冰表面准液体层的物理性质和过冷水形成冰晶的过程。最重要的论点是我们展示了冰的基面和棱柱面界面之间的各向异性生长模式。在此国际项目期间取得的成果的基础上，我们开始开发一种新的冰晶图案形成模型。在项目期间，在札幌也举行了两次关于多面晶体图案形成的相关研讨会。50多名研究人员参与了这两项研究。

Pattern formation mechanisms of ice crystals with the faceted faces were carried out in cooperation with the researchers of Carnegie-Mellon Univ. Pittsburgh.First of all, pattern formation of ice crystal interface during the one-directional growth was observed in-situ using a Mach-Zehnde interferometer. A direct evidence for the constitutional supercooling, which develops in front of the interface, was first given from the analysis of diffusion field of impurity using the interference fringes. The Mullins-Sekerka instability theory, which is basically a linear and steady state theory, is also applicable to the pattern formation of ice interface.Second, a new model for the ice disk growth of ice in the supercooled water was also developed on the basis of the experimental results for ice crystal growth.As a result, we showed that there are two different modes for ice crystal processes in the supercooled water depending on the growth kinetics of basal faces (namely, the spiral growth or the two-dimensional nucleation growth of basal faces). This result gives the new prospect for the understanding of the pattern formation of crystals with faceted faces.Third, the molecular dynamics simulations were .also carried out for the ice surfaces and the ice-water interfaces. The physical properties of quasi-liquid layers on the ice surfaces and the growth processes of ice crystals from the supercooled water were precisely discussed in the molecular level. Most important argument was that we showed the anisotropic growth modes between basal and prismatic interfaces of ice. We begin to develop a new model for the pattern formation of ice crystal on the basis of these results obtained in the period of this international project. Related symposiums about the pattern formation of crystals with faceted faces were also held in Sapporo twice during the project periods. More than 50 researchers were participated for both.