Prediction of CH4 and CO2 hydrate phase equilibrium and cage occupancy from ab initio intermolecular potentials
Prediction of CH4 and CO2 hydrate phase equilibrium and cage occupancy from ab initio intermolecular potentials
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DOI：
10.1016/j.gca.2005.05.012
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发表时间：
2005-09
影响因子：
5
通讯作者：
Rui Sun;Zhenhao Duan
中科院分区：
文献类型：
--
作者：
Rui Sun;Zhenhao Duan
提出了一种改进的预测水体系中ch4和co2水合物相平衡和笼占率的模型。与大多数水合物模型采用Kihara势或Lennard-Jones势（参数来源于水合物的实验相平衡数据）不同，我们使用原子位-位势来解释与角相关的分子相互作用，参数直接来自从头算结果。由于这种处理，我们的模型可以在很宽的温度-压力范围内（从243-318 K， ch4水合物从10-3000 bar；从253-293 K， co2水合物从5-2000 bar）预测二元体系中ch4水合物和co2水合物的相平衡，精度接近实验。对于给定温度下的压力，该模型与实验数据的平均偏差小于3%。这种精度与以前的压力低于500bar的模型相似，但在更高的压力下比以前的模型更准确。该模型还可以在不拟合任何实验数据的情况下预测ch4水合物和co2水合物的笼占率和水化数。这项研究的成功验证了从头算分子间势对热力学性质的可预测性。
Presented is an improved model for the prediction of phase equilibria and cage occupancy of CH4and CO2hydrate in aqueous systems. Different from most hydrate models that employ Kihara potential or Lennard-Jones potential with parameters derived from experimental phase equilibrium data of hydrates, we use atomic site-site potentials to account for the angle-dependent molecular interactions with parameters directly from ab initio calculation results. Because of this treatment, our model can predict the phase equilibria of CH4hydrate and CO2hydrate in binary systems over a wide temperature-pressure range (from 243–318 K, and from 10–3000 bar for CH4hydrate; from 253–293 K, and from 5–2000 bar for CO2hydrate) with accuracy close to experiment. The average deviation of this model from experimental data is less than 3% in pressures for a given temperature. This accuracy is similar to previous models for pressures below 500 bar, but is more accurate than previous models at higher pressures. This model is also capable of predicting the cage occupancy and hydration number for CH4hydrate and CO2hydrate without fitting any experimental data. The success of this study validates the predictability of ab initio intermolecular potentials for thermodynamic properties.