Müller Erich A, Jackson George
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom; email:
Annu Rev Chem Biomol Eng. 2014;5:405-27. doi: 10.1146/annurev-chembioeng-061312-103314. Epub 2014 Mar 31.
A description of fluid systems with molecular-based algebraic equations of state (EoSs) and by direct molecular simulation is common practice in chemical engineering and the physical sciences, but the two approaches are rarely closely coupled. The key for an integrated representation is through a well-defined force field and Hamiltonian at the molecular level. In developing coarse-grained intermolecular potential functions for the fluid state, one typically starts with a detailed, bottom-up quantum-mechanical or atomic-level description and then integrates out the unwanted degrees of freedom using a variety of techniques; an iterative heuristic simulation procedure is then used to refine the parameters of the model. By contrast, with a top-down technique, one can use an accurate EoS to link the macroscopic properties of the fluid and the force-field parameters. We discuss the latest developments in a top-down representation of fluids, with a particular focus on a group-contribution formulation of the statistical associating fluid theory (SAFT-γ). The accurate SAFT-γ EoS is used to estimate the parameters of the Mie force field, which can then be used with confidence in direct molecular simulations to obtain thermodynamic, structural, interfacial, and dynamical properties that are otherwise inaccessible from the EoS. This is exemplified for several prototypical fluids and mixtures, including carbon dioxide, hydrocarbons, perfluorohydrocarbons, and aqueous surfactants.
使用基于分子的状态代数方程（EoSs）并通过直接分子模拟来描述流体系统，在化学工程和物理科学中是常见的做法，但这两种方法很少紧密结合。实现综合表示的关键在于分子水平上定义明确的力场和哈密顿量。在开发用于流体状态的粗粒度分子间势函数时，通常从详细的自下而上的量子力学或原子水平描述开始，然后使用各种技术消除不需要的自由度；接着使用迭代启发式模拟程序来优化模型参数。相比之下，采用自上而下的技术，可以使用精确的EoS将流体的宏观性质与力场参数联系起来。我们讨论了流体自上而下表示的最新进展，特别关注统计缔合流体理论（SAFT-γ）的基团贡献公式。精确的SAFT-γ EoS用于估计米氏力场的参数，然后可以放心地将其用于直接分子模拟，以获得EoS无法获得的热力学、结构、界面和动力学性质。这在几种典型流体和混合物中得到了例证，包括二氧化碳、碳氢化合物、全氟碳氢化合物和水性表面活性剂。
