Anisotropic Growth Kinetics and Pattern Formation of Ice

与卡内基-梅隆大学的研究人员合作，研究了具有刻面的冰晶的图案形成机制。首先，利用马赫-曾德干涉仪对单向生长过程中冰晶界面图案的形成进行了原位观测。通过干涉条纹对杂质扩散场的分析，首次给出了界面前方成分过冷的直接证据。Mullins-Sekerka不稳定性理论基本上是一个线性的稳态理论，它同样适用于冰界面图案的形成。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，过冷水中冰晶体的生长过程有两种不同的模式，这取决于基面的生长动力学(即基面的螺旋生长或二维成核生长)。这一结果为理解多面晶体的花样形成提供了新的前景。第三，还对冰面和冰-水界面进行了分子动力学模拟。在分子水平上精确地讨论了冰表面准液态层的物理性质和过冷水中冰晶的生长过程。最重要的论点是，我们展示了冰的基面和棱柱面之间的各向异性生长模式。在此基础上，我们开始发展冰晶花样形成的新模型。在项目期间，还在札幌举行了两次关于多面晶体图案形成的相关专题讨论会。这两项研究都有50多名研究人员参与。

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.