Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Chem Phys. 2017 Apr 21;146(15):154102. doi: 10.1063/1.4979896.
We present an empirical potential-based quasi-continuum theory (EQT) to predict the structure and thermodynamic properties of confined fluid mixtures. The central idea in the EQT is to construct potential energies that integrate important atomistic details into a continuum-based model such as the Nernst-Planck equation. The EQT potentials can be also used to construct the excess free energy functional, which is required for the grand potential in the classical density functional theory (cDFT). In this work, we use the EQT-based grand potential to predict various thermodynamic properties of a confined binary mixture of hydrogen and methane molecules inside graphene slit channels of different widths. We show that the EQT-cDFT predictions for the structure, surface tension, solvation force, and local pressure tensor profiles are in good agreement with the molecular dynamics simulations. Moreover, we study the effect of different bulk compositions and channel widths on the thermodynamic properties. Our results reveal that the composition of methane in the mixture can significantly affect the ordering of molecules and thermodynamic properties under confinement. In addition, we find that graphene is selective to methane molecules.
我们提出了一种基于经验势的拟连续体理论（EQT）来预测受限流体混合物的结构和热力学性质。EQT 的核心思想是构建势能，将重要的原子细节整合到连续体模型中，如 Nernst-Planck 方程。EQT 势能也可用于构建超额自由能泛函，这是经典密度泛函理论（cDFT）中grand 势所必需的。在这项工作中，我们使用基于 EQT 的 grand 势来预测不同宽度的石墨烯狭缝通道内受限的氢和甲烷分子二元混合物的各种热力学性质。我们表明，EQT-cDFT 对结构、表面张力、溶剂化力和局部压力张量分布的预测与分子动力学模拟吻合良好。此外，我们研究了不同的体组成和通道宽度对热力学性质的影响。我们的结果表明，混合物中甲烷的组成可以显著影响受限条件下分子的有序性和热力学性质。此外，我们发现石墨烯对甲烷分子具有选择性。
