Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, USA.
J Chem Phys. 2016 Dec 7;145(21):211924. doi: 10.1063/1.4966018.
Heterogeneous ice nucleation is the primary pathway for ice formation. However, the detailed molecular mechanisms by which surfaces promote or hinder ice nucleation are not well understood. We present results from extensive molecular dynamics simulations of ice nucleation near modified silver iodide (AgI) surfaces. The AgI surfaces are modified to investigate the effects of the surface charge distribution on the rate of ice nucleation. We find that the surface charge distribution has significant effects on ice nucleation. Specifically, AgI surfaces with the positive charges above the negative charges in the surface promote ice nucleation, while ice nucleation is hindered for surfaces in which the negative charges are above or in-plane with the positive charges. The structure of water molecules in the interfacial region as measured by the orientations of the water molecules relative to the surface can explain the differences in the ice nucleation at the different surfaces. We suggest that the distributions of the orientations of the interfacial water molecules could be used more broadly as a measure of ice nucleating propensity.
非均相冰核化是冰形成的主要途径。然而，表面促进或阻碍冰核化的详细分子机制尚不清楚。我们展示了在经过修饰的碘化银（AgI）表面附近冰核化的广泛分子动力学模拟的结果。对 AgI 表面进行了修饰，以研究表面电荷分布对冰核化速率的影响。我们发现表面电荷分布对冰核化有显著影响。具体来说，表面上带正电荷的 AgI 表面比带负电荷的 AgI 表面更有利于冰核化，而带负电荷的 AgI 表面或与带正电荷的 AgI 表面共面时会阻碍冰核化。通过测量水分子相对于表面的取向，可以得到界面区域水分子的结构，从而解释不同表面上冰核化的差异。我们认为，界面水分子取向的分布可以更广泛地用作衡量冰核化倾向的指标。
