Equilibrium shape of ice Ih and roughening transition of prism facet

我们研究了高压下冰h沿融化曲线的平衡形状。在-15℃和1600 bar的温度下，平衡态由圆盘向六角形板转变。这表示在该点上棱柱面发生了粗化过渡。在粗化点附近，生长形状和熔化形状表现为六角形各向异性，而平衡形状为圆形各向同性。此外，它们的六边形方向被旋转了30°。三种形状在粗化点附近不同。我们还测量了冰在水中既不生长也不融化的融化曲线；结果表明，在-15℃和1600 bar温度下，熔点曲线出现了不连续现象。粗化点和不连续点吻合较好。这是令人困惑的，因为粗化转变是二级相变，对熔化曲线没有影响。如果不连续性与粗化无关，则可以归因于冰或水中的某种相变，而不是在冰/水界面中进行粗化。

We have investigated equilibrium shape of ice Ih along the melting curve under high pressures. The equilibrium shape showed phase transition from a circular disk to a hexagonal plate at -15℃ and 1600 bar. This represents that roughening transition occurred on prism facets at the point. However, growth and melting shapes exhibited hexagonal anisotropy near the roughening point, whereas equilibrium shape was circular and isotropic. In addition, their hexagonal orientations were rotated by 30°. Three shapes were different near the roughening point.We also have measured the melting curve on which ice neither grows nor melts in water ; as a result, there was a discontinuity on the melting curve at -15℃ and 1600 bar. The roughening and discontinuity points agree well. This is puzzling, because roughening transition is the second-order phase transition and affects nothing on the melting curve. If the discontinuity has no relation with roughening, it can be attributable to some phase transition in ice or water, not in an ice/water interface for roughening.