Self-diffusion coefficient and viscosity of methane and carbon dioxide via molecular dynamics simulations based on new ab initio-derived force fields
Self-diffusion coefficient and viscosity of methane and carbon dioxide via molecular dynamics simulations based on new ab initio-derived force fields
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DOI：
10.1016/j.fluid.2018.10.011
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发表时间：
2019-02-15
影响因子：
2.6
通讯作者：
Froeba, Andreas P.
中科院分区：
文献类型：
--
作者：
Higgoda, Ubaya A.;Hellmann, Robert;Froeba, Andreas P.
在本研究中，自扩散系数和粘度的甲烷（CH 4）和二氧化碳（CO2）的过热蒸汽，气态和超临界状态下的分子动力学（MD）模拟研究。用于MD模拟的参数基于新的分子力场（FF），该分子力场是根据先前开发的、基于零密度极限下从头计算的相互作用能的高度准确的对势推导出来的。使用这些优化的刚性全原子FF，进行了几μ s量级的多次MD模拟运行，以根据压力自相关函数的时间积分平台和线性爱因斯坦区域的自扩散系数来评估动态粘度。对于后者的属性，它示出的叶-胡默校正占稠密液体系统中的流体动力学制度的有限盒大小的影响，可以一致地转移到气体系统在各种密度。从我们的从头计算得到的FF与从已建立的文献FF得到的模拟动力学性质的比较表明，我们建议的方法是上级其他刚性的全原子的方法，特别是灵活的和联合原子模型对应的密度范围内的压力在0.1和10 MPa之间。对于温度为295，325，和355 K，我们的模拟结果的产品的自扩散系数和密度，以及平均扩展的统计不确定性（k = 2）为0.6%和8.0%，分别为动态粘度，代表密度依赖性的两个属性，并同意在文献中的一些模拟和实验数据。(C)2018爱思唯尔B. V.保留所有权利。
In the present study, the self-diffusion coefficient and viscosity of methane (CH4) and carbon dioxide (CO2) were studied by molecular dynamics (MD) simulations in the superheated vapor, gaseous, and supercritical state. The parameters used for the MD simulations are based on new molecular force fields (FFs), which were derived from previously developed, highly accurate pair potentials based on ab initio-calculated interaction energies in the limit of zero density. Using these optimized rigid all-atom FFs, multiple MD simulation runs in the order of several mu s were performed to evaluate the dynamic viscosity from the plateau of the time integral of the pressure autocorrelation function and the self-diffusion coefficient from the linear Einstein regime. For the latter property, it is shown that the Yeh-Hummer correction accounting for effects of the finite box size for dense liquid systems in the hydrodynamic regime can be transferred consistently to gaseous systems at various densities. A comparison of the simulated dynamical properties obtained from our ab initio-derived FFs with those obtained from established literature FFs showed that our suggested approach is superior to the other rigid all-atom approaches and in particular to flexible and united-atom models over density ranges corresponding to pressures between 0.1 and 10 MPa. For temperatures of 295, 325, and 355 K, our simulation results for the product of self-diffusion coefficient and density as well as for the dynamic viscosity with average expanded statistical uncertainties (k = 2) of 0.6% as well as 8.0%, respectively, represent the density dependency of both properties and agree with the few simulation and experimental data available in the literature. (C) 2018 Elsevier B.V. All rights reserved.