The energy density of water and ice nucleation.
The energy density of water and ice nucleation.
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DOI：
10.1126/science.259.5100.1469
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发表时间：
1993-03
期刊：
影响因子：
56.9
通讯作者：
L. Wilen
中科院分区：
文献类型：
--
作者：
L. Wilen
M.Gavish等人。假设(1)成核是由在极性晶体的窄裂缝中发现的大电场引起的。他们的计算表明，冰的双层结构在D-丙氨酸晶体缝隙中比在D，L-丙氨酸晶体缝隙中具有更高的能量，因此他们得出结论，后者有利于成核。然而，与成核过程相关的是冰核的能量密度与每种晶体缝隙中水的能量密度之间的差异。此外，双层冰核不太可能是这种冰核的形状，因为与冰和过冷水之间的化学势差导致的自由能增加相比，表面能量的成本很高。报告中描述的双层原子核相对于水肯定是不稳定的，除非冰优先湿润晶体的表面。这将构成表面冻结，这与自然界观察到的通常的冰表面融化不一致(2)。可以估计一个小的球形冰核(3)与电场中相同体积的水之间的静电能量密度(W)之差。在杰克逊(4)之后，人们可以写
M. Gavish et al. hypothesize (1) that nucleation is induced by large electric fields found in the narrow cracks of polar crystals. Their calculations show that an ice bilayer structure has a higher energy in a D-alanine crystal crevice than in a D, L-alanine crystal crevice, so they conclude that nucleation is facilitated by the latter crystals. What is pertinent to the nucleation process, how-ever, is the difference between the energy density of an ice nucleus and that of water in the crevice of each kind of crystal. Furthermore, a bilayer is not a likely shape for such an ice nucleus because of the heavy cost of surface energy relative to the gain in free energy that results from the chemical potential difference between ice and supercooled water. The bilayer nucleus described in the report would certainly be unstable relative to water unless ice preferentially wet the surface of the crystals. This would constitute surface freezing, which is not consistent with the usual surface melting of ice observed in nature (2). An estimate can be made of the difference in the electrostatic energy density (W) between a small spherical ice nucleus (3) and the same volume of water in an electric field. Following Jackson (4), one can write