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Markov state model of the two-state behaviour of water
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2016-10-03 15:15:58 , DOI: 10.1063/1.4963305 Peter Hamm 1
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2016-10-03 15:15:58 , DOI: 10.1063/1.4963305 Peter Hamm 1
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With the help of a Markov State Model (MSM), two-state behaviour is resolved for two computer models of water in a temperature range from 255 K to room temperature (295 K). The method is first validated for ST2 water, for which the so far strongest evidence for a liquid-liquid phase transition exists. In that case, the results from the MSM can be cross-checked against the radial distribution function g 5(r) of the 5th-closest water molecule around a given reference water molecule. The latter is a commonly used local order parameter, which exhibits a bimodal distribution just above the liquid-liquid critical point that represents the low-density form of the liquid (LDL) and the high density liquid. The correlation times and correlation lengths of the corresponding spatial domains are calculated and it is shown that they are connected via a simple diffusion model. Once the approach is established, TIP4P/2005 will be considered, which is the much more realistic representation of real water. The MSM can resolve two-state behavior also in that case, albeit with significantly smaller correlation times and lengths. The population of LDL-like water increases with decreasing temperature, thereby explaining the density maximum at 4 °C along the lines of the two-state model of water.
中文翻译：
水的两态行为的马尔可夫状态模型
借助马尔可夫状态模型（MSM），可以解决两个计算机模型的水在255 K到室温（295 K）范围内的两种状态行为。该方法首先针对ST2水进行了验证，迄今为止，ST2水存在着最强有力的液-液相转变证据。在这种情况下，可以对照径向分布函数g 5（r给定参考水分子附近的第5个最接近的水分子）。后者是常用的局部参数，它在液-液临界点正上方显示双峰分布，该临界点表示液体（LDL）和高密度液体的低密度形式。计算了相应空间域的相关时间和相关长度，结果表明它们之间通过简单的扩散模型相连。一旦确定了方法，将考虑TIP4P / 2005，这是对真实水的更现实的表示。即使在这种情况下，MSM也可以解决两种状态的行为，尽管相关时间和长度明显缩短。LDL样水的数量随着温度的降低而增加，
更新日期：2016-10-04
中文翻译：
水的两态行为的马尔可夫状态模型
借助马尔可夫状态模型（MSM），可以解决两个计算机模型的水在255 K到室温（295 K）范围内的两种状态行为。该方法首先针对ST2水进行了验证，迄今为止，ST2水存在着最强有力的液-液相转变证据。在这种情况下，可以对照径向分布函数g 5（r给定参考水分子附近的第5个最接近的水分子）。后者是常用的局部参数，它在液-液临界点正上方显示双峰分布，该临界点表示液体（LDL）和高密度液体的低密度形式。计算了相应空间域的相关时间和相关长度，结果表明它们之间通过简单的扩散模型相连。一旦确定了方法，将考虑TIP4P / 2005，这是对真实水的更现实的表示。即使在这种情况下，MSM也可以解决两种状态的行为，尽管相关时间和长度明显缩短。LDL样水的数量随着温度的降低而增加，
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