Ren Yi, Bertram Allan K, Patey G N
Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1.
J Phys Chem B. 2020 Jun 4;124(22):4605-4618. doi: 10.1021/acs.jpcb.0c01695. Epub 2020 May 26.
Molecular dynamics simulations are employed to investigate the influence of inorganic salts on ice nucleation by the Al surface of kaolinite, terminated with hydroxyl groups. Seven salt solutions (LiI(Cl), NaI(Cl), KI(Cl), and NHI) are considered. Simulations were performed at 300 K to obtain equilibrium surface-ion and surface-water density profiles. These simulations show no specific ion adsorption at the kaolinite surface. There are weak surface-ion correlations, with cations preferring to be closer to the surface than the anions. At a supercooling of 26 K (taking account of freezing point depression), 1 M salt solutions slowed ice nucleation by a factor of 2-3 compared with pure water and significantly reduced the rate of ice growth after nucleation. All salt solutions had similar influences on ice nucleation, and no specific ion effects were identified. Ice nucleation simulations for 1 M NaI(Cl), KI(Cl), and LiI solutions were performed for a range of temperatures. In all cases, the supercooling required for ice nucleation was larger by ∼1-6 K, after accounting for freezing point depression, than that required for pure water. For 1 M LiI solution an earlier laboratory study using kaolin as ice nucleating particles (INP) reported that the supercooling required for ice nucleation was ∼11 K smaller than that required for pure water. Our simulation results are not consistent with this finding. In this paper, we report new laboratory results for 1 M LiI solution employing kaolinite as INP. In our experiments ice nucleation in the LiI solution required the same supercooling as pure water, which is more consistent with our simulations.
采用分子动力学模拟研究无机盐对高岭石铝表面（以羟基封端）冰核形成的影响。考虑了七种盐溶液（LiI(Cl)、NaI(Cl)、KI(Cl)和NHI）。在300 K下进行模拟以获得平衡表面离子和表面水密度分布。这些模拟表明在高岭石表面没有特定的离子吸附。存在较弱的表面离子相关性，阳离子比阴离子更倾向于靠近表面。在过冷26 K（考虑冰点降低）时，与纯水相比，1 M盐溶液使冰核形成速度减慢了2至3倍，并显著降低了成核后冰的生长速度。所有盐溶液对冰核形成的影响相似，未发现特定的离子效应。对1 M NaI(Cl)、KI(Cl)和LiI溶液在一系列温度下进行了冰核形成模拟。在所有情况下，考虑冰点降低后，冰核形成所需的过冷度比纯水所需的过冷度大~1 - 6 K。对于1 M LiI溶液，一项早期的实验室研究使用高岭土作为冰核粒子（INP），报告称冰核形成所需的过冷度比纯水所需的过冷度小约11 K。我们的模拟结果与这一发现不一致。在本文中，我们报告了使用高岭石作为INP的1 M LiI溶液的新实验室结果。在我们的实验中，LiI溶液中的冰核形成所需的过冷度与纯水相同，这与我们的模拟结果更一致。
