单原子水分子模型冰均相成核的自由能景观。

Free energy landscapes for homogeneous nucleation of ice for a monatomic water model.

机构信息

Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom.

出版信息

J Chem Phys. 2012 Feb 7;136(5):054501. doi: 10.1063/1.3677192.

DOI:10.1063/1.3677192

PMID:22320745

Abstract

We simulate the homogeneous nucleation of ice from supercooled liquid water at 220 K in the isobaric-isothermal ensemble using the MW monatomic water potential. Monte Carlo simulations using umbrella sampling are performed in order to determine the nucleation free energy barrier. We find the Gibbs energy profile to be relatively consistent with that predicted by classical nucleation theory; the free energy barrier to nucleation was determined to be ~18 k(B)T and the critical nucleus comprised ~85 ice particles. Growth from the supercooled liquid gives clusters that are predominantly cubic, whilst starting with a pre-formed subcritical nucleus of cubic or hexagonal ice results in the growth of predominantly that phase of ice only.

摘要

我们在等压等温热力学系综中使用 MW 单原子水势模拟了 220 K 过冷水的均相成核。为了确定成核自由能势垒，我们进行了使用伞形采样的蒙特卡罗模拟。我们发现吉布斯能量分布与经典成核理论预测的相对一致；成核的自由能势垒约为 18 k(B)T，临界核包含约 85 个冰粒子。从过冷液体开始生长得到的团簇主要是立方的，而从预先形成的立方或六方冰的亚临界核开始则导致仅生长出该相的冰。