CAN THE DENSITY MAXIMUM OF WATER BE FOUND BY COMPUTER-SIMULATION
CAN THE DENSITY MAXIMUM OF WATER BE FOUND BY COMPUTER-SIMULATION
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DOI：
10.1063/1.467029
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发表时间：
1994-05-01
影响因子：
4.4
通讯作者：
VANGUNSTEREN, WF
中科院分区：
文献类型：
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作者：
BILLETER, SR;KING, PM;VANGUNSTEREN, WF
路径积分分子动力学（PIMD）模拟的扩展的简单点电荷（SPC/E）模型的液态水（H2O和D2 O）已被执行，以找到在该温度下获得最大的液体密度。为了比较，纯经典的SPC和SPC/E水也被模拟了很长一段时间（超过200 ps）。结构性能和各种温度依赖量的报告。特别注意的压力和体积的波动，在典型的（常数NVT）和等温等压（常数NPT）合奏，分别模拟运行。虽然通过监测作为温度的函数的能量-体积相关性来检测密度最大值，但是相关性中的大的统计不确定性降低了这一发现的意义。这项工作的主要结论有三个方面。首先，使用能量-体积相关矩来确定密度最大值似乎是一种有用的方法，尽管在相当宽的温度范围内进行0.5-1.0 ns之间的大量非常长的模拟是获得准确结果所必需的。其次，SPC和SPC/E水模型都不能准确地再现冷水的密度。最后，水模型的量子力学处理是必要的，以正确地表示凝聚相的结构，能量和波动。
Path integral molecular dynamics (PIMD) simulations of the extended simple point charge (SPC/E) model of liquid water (both H2O and D2O) have been performed in order to find the temperature at which the maximum liquid density is obtained. For comparison, purely classical SPC and SPC/E water have also been simulated over long periods (more than 200 ps). Structural properties and various temperature dependent quantities are reported. Special attention has been given to the fluctuations of pressure and volume in simulations run in the canonical (constant NVT) and isothermal-isobaric (constant NPT) ensembles, respectively. Although a density maximum is detected by monitoring energy-volume correlations as a function of temperature, the large statistical uncertainty in the correlations reduces the significance of this finding. The main conclusions of this work are threefold. First, the use of the energy-volume correlation moment to determine the density maximum appears to be a useful method, although a number of very long simulations of between 0.5-1.0 ns over a fairly wide temperature range are necessary to obtain accurate results. Second, neither the SPC nor the SPC/E water models ate able to reproduce the density of cold water accurately. Finally, a quantum mechanical treatment of the water model is necessary to correctly represent the structure, energy, and fluctuations of the condensed phase.