Departamento de Quimica Fisica, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid, Spain and Departamento de Fisica Aplicada I , Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
J Chem Phys. 2016 Dec 7;145(21):211922. doi: 10.1063/1.4965427.
By using the seeding technique the nucleation rate for the formation of ice at room pressure will be estimated for the TIP4P/ICE model using longer runs and a smaller grid of temperatures than in the previous work. The growth rate of ice will be determined for TIP4P/ICE and for the mW model of water. Although TIP4P/ICE and mW have a similar melting point and melting enthalpy, they differ significantly in the dynamics of freezing. The nucleation rate of mW is lower than that of TIP4P/ICE due to its higher interfacial free energy. Experimental results for the nucleation rate of ice are between the predictions of these two models when obtained from the seeding technique, although closer to the predictions of TIP4P/ICE. The growth rate of ice for the mW model is four orders of magnitude larger than for TIP4P/ICE. Avrami's expression is used to estimate the crystallization time from the values of the nucleation and growth rates. For mW the minimum in the crystallization time is found at approximately 85 K below the melting point and its value is of about a few ns, in agreement with the results obtained from brute force simulations by Moore and Molinero. For the TIP4P/ICE the minimum is found at about 55 K below the melting point, but its value is about ten microseconds. This value is compatible with the minimum cooling rate required to avoid the formation of ice and obtaining a glass phase. The crossover from the nucleation controlled crystallization to the growth controlled crystallization will be discussed for systems of finite size. This crossover could explain the apparent discrepancy between the values of J obtained by different experimental groups for temperatures below 230 K and should be considered as an alternative hypothesis to the two previously suggested: internal pressure and/or surface freezing effects. A maximum in the compressibility was found for the TIP4P/ICE model in supercooled water. The relaxation time is much smaller than the crystallization time at the temperature at which this maximum occurs, so this maximum is a real thermodynamic feature of the model. At the temperature of minimum crystallization time, the crystallization time is larger than the relaxation time by just two orders of magnitude.
使用成核技术，我们将使用更长的运行时间和更小的温度网格来估计 TIP4P/ICE 模型在室温下形成冰的成核速率，而不是之前的工作。我们将确定 TIP4P/ICE 和 mW 水模型的冰生长速率。尽管 TIP4P/ICE 和 mW 的熔点和熔化焓相似，但它们在冻结动力学方面有很大的不同。由于界面自由能较高，mW 的成核速率低于 TIP4P/ICE。通过成核技术获得的实验结果表明，mW 的成核速率在这两种模型的预测之间，尽管更接近 TIP4P/ICE 的预测。mW 模型的冰生长速率比 TIP4P/ICE 大四个数量级。Avrami 表达式用于根据成核和生长速率的值估计结晶时间。对于 mW，在熔点以下约 85 K 处发现结晶时间的最小值，其值约为几个纳秒，与 Moore 和 Molinero 通过暴力模拟获得的结果一致。对于 TIP4P/ICE，最小值出现在熔点以下约 55 K 处，但值约为 10 微秒。这个值与避免形成冰并获得玻璃相所需的最小冷却速率兼容。我们将讨论有限大小系统中成核控制结晶向生长控制结晶的转变。这种转变可以解释不同实验小组在 230 K 以下温度下获得的 J 值之间的明显差异，并且可以作为之前提出的两个假设（内部压力和/或表面冻结效应）的替代假设。在过冷水中，我们发现 TIP4P/ICE 模型的压缩性有一个最大值。弛豫时间远小于在发生最大值的温度下的结晶时间，因此这个最大值是模型的真实热力学特征。在最小结晶时间的温度下，结晶时间比弛豫时间仅大两个数量级。
