Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
J Chem Phys. 2013 Oct 14;139(14):144501. doi: 10.1063/1.4824139.
Molecular dynamics simulations are employed to show that electric field bands acting only over a portion of a surface can function as effective ice nuclei. Field bands of different geometry (rectangular, triangular, and semicircular cross sectional areas are considered) all nucleate ice, provided that the band is sufficiently large. Rectangular bands are very efficient if the width and thickness are ≳0.35 nm, and ≳0.15 nm, respectively, and the necessary dimensions are comparable for other geometries. From these simulations we also learn more about the ice nucleation and growth process. Careful analysis of different systems reveals that ice strongly prefers to grow at (111) planes of cubic ice. This agrees with an earlier theoretical deduction based on considerations of water-ice interfacial energies. We find that ice nucleated by field bands usually grows as a mixture of cubic and hexagonal ice, consistent with other simulations of ice growth, and with experiment. This contrasts with simulations carried out with nucleating fields that span the entire surface area, where cubic ice dominates, and hexagonal layers are very rarely observed. We argue that this discrepancy is a simulation artifact related to finite sample size and periodic boundary conditions.
采用分子动力学模拟表明，仅在表面一部分上起作用的电场带可以作为有效的冰核。不同几何形状的场带（考虑了矩形、三角形和半圆形的横截面面积）都能成核冰，只要带足够大。如果矩形带的宽度和厚度分别约为 0.35nm 和 0.15nm，则矩形带非常有效，其他几何形状的必要尺寸也相当。从这些模拟中，我们还可以更多地了解冰成核和生长过程。对不同系统的仔细分析表明，冰强烈倾向于在立方冰的（111）面上生长。这与基于水-冰界面能考虑的早期理论推导一致。我们发现，电场带成核的冰通常生长为立方冰和六方冰的混合物，这与其他冰生长的模拟结果以及实验结果一致。这与跨越整个表面积的成核场进行的模拟形成对比，在跨越整个表面积的模拟中，立方冰占主导地位，很少观察到六方层。我们认为这种差异是与有限的样本尺寸和周期性边界条件有关的模拟伪影。
