Molecular Simulation of the Phase Diagram of Methane Hydrate: Free Energy Calculations, Direct Coexistence Method, and Hyperparallel Tempering.
Molecular Simulation of the Phase Diagram of Methane Hydrate: Free Energy Calculations, Direct Coexistence Method, and Hyperparallel Tempering.
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DOI：
10.1021/acs.langmuir.7b02238
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发表时间：
2017-08
期刊：
影响因子：
--
通讯作者：
Dongliang Jin;B. Coasne
中科院分区：
文献类型：
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作者：
Dongliang Jin;B. Coasne
采用不同的分子模拟策略来评估甲烷水合物在不同温度和压力条件下的稳定性。首先，利用两种水分子模型，采用爱因斯坦分子法组成的自由能计算与半零元蒙特卡罗模拟相结合的方法，确定了甲烷水合物的压力-温度相图。通过这些计算，我们还估计了水和甲烷的化学势以及共存时甲烷的占比。其次，我们还考虑了另外两种可以探测甲烷水合物相图的先进分子模拟技术：大正则系综中的直接共存方法和超平行回火蒙特卡罗方法。发现这两种直接技术提供了与使用严格的自由能计算得到的压力-温度相图一致的稳定条件。本工作得到的相图与以往的模拟研究一致，在使用TIP4P/Ice模型描述水分子的情况下，与实验相图接近。
Different molecular simulation strategies are used to assess the stability of methane hydrate under various temperature and pressure conditions. First, using two water molecular models, free energy calculations consisting of the Einstein molecule approach in combination with semigrand Monte Carlo simulations are used to determine the pressure-temperature phase diagram of methane hydrate. With these calculations, we also estimate the chemical potentials of water and methane and methane occupancy at coexistence. Second, we also consider two other advanced molecular simulation techniques that allow probing the phase diagram of methane hydrate: the direct coexistence method in the Grand Canonical ensemble and the hyperparallel tempering Monte Carlo method. These two direct techniques are found to provide stability conditions that are consistent with the pressure-temperature phase diagram obtained using rigorous free energy calculations. The phase diagram obtained in this work, which is found to be consistent with previous simulation studies, is close to its experimental counterpart provided the TIP4P/Ice model is used to describe the water molecule.