The A in SAFT: developing the contribution of association to the Helmholtz free energy within a Wertheim TPT1 treatment of generic Mie fluids
The A in SAFT: developing the contribution of association to the Helmholtz free energy within a Wertheim TPT1 treatment of generic Mie fluids
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DOI：
10.1080/00268976.2015.1029027
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发表时间：
2015-05-19
影响因子：
1.7
通讯作者：
Jackson, George
中科院分区：
文献类型：
--
作者：
Dufal, Simon;Lafitte, Thomas;Jackson, George
分子缔合的精确表示是高级状态方程（EOSs）的重要组成部分，它提供了对氢键起重要作用的复杂流体的热力学性质的描述。Wertheim的缔合体系的一阶热力学微扰理论（TPT 1）与单体流体的结构和热力学性质的精确描述相结合，构成了统计缔合流体理论（SAFT）的基础。在SAFT和相关的EOSs的自由能协会的贡献是非常敏感的性质的分子间的潜力来描述的单体，至关重要的是，热力学和结构性质的代表性的准确性。在这里，我们开发了一个准确的描述的关联贡献内使用最近开发的SAFT-VR米氏框架的链分子形成的片段通过米氏势相互作用[T。Lafitte，A.阿波斯托拉库角A，C. S. Escheriman，E. A. Muller和G.杰克逊，化学物理学杂志139，154504（2013）]。由于Mie相互作用是一种软核势模型，因此采用了类似于Lennard-Jones势[E. A. Muller和K. E. Gubbins，Ind.Eng.Chem.Res.34，3662（1995）]来描述缔合对亥姆霍兹自由能的贡献。的径向分布函数（RDF）的米氏流体（这是所需的评估在心脏的关联项的积分）确定了广泛的热力学条件（温度和密度）使用参考超网状链（RHNC）积分方程理论。具有不同的关联几何形状的米氏流体的关联内核的数值数据，然后相关的热力学状态的范围内，以获得关联的贡献，可以应用于不同的值的米氏排斥指数的一般表达式。由此产生的SAFT-VR米氏状态方程允许汽液平衡和单相性质的关联流体，如水，甲醇，氨，硫化氢，和它们的混合物的一个大大改善的描述。还进行了比较之间的理论预测的关联度为水和氢键的程度从SPC/E和TIP 4P/2005原子模型的分子模拟。
An accurate representation of molecular association is a vital ingredient of advanced equations of state (EOSs), providing a description of thermodynamic properties of complex fluids where hydrogen bonding plays an important role. The combination of the first-order thermodynamic perturbation theory (TPT1) of Wertheim for associating systems with an accurate description of the structural and thermodynamic properties of the monomer fluid forms the basis of the statistical associating fluid theory (SAFT) family of EOSs. The contribution of association to the free energy in SAFT and related EOSs is very sensitive to the nature of intermolecular potential used to describe the monomers and, crucially, to the accuracy of the representation of the thermodynamic and structural properties. Here we develop an accurate description of the association contribution for use within the recently developed SAFT-VR Mie framework for chain molecules formed from segments interacting through a Mie potential [T. Lafitte, A. Apostolakou, C. Avendano, A, Galindo, C. S. Adjiman, E. A. Muller, and G. Jackson, J. Chem. Phys. 139, 154504 (2013)]. As the Mie interaction represents a soft-core potential model, a method similar to that adopted for the Lennard-Jones potential [E. A. Muller and K. E. Gubbins, Ind. Eng. Chem. Res. 34, 3662 (1995)] is employed to describe the association contribution to the Helmholtz free energy. The radial distribution function (RDF) of the Mie fluid (which is required for the evaluation of the integral at the heart of the association term) is determined for a broad range of thermodynamic conditions (temperatures and densities) using the reference hyper-netted chain (RHNC) integral-equation theory. The numerical data for the association kernel of Mie fluids with different association geometries are then correlated for a range of thermodynamic states to obtain a general expression for the association contribution which can be applied for varying values of the Mie repulsive exponent. The resulting SAFT-VR Mie EOS allows for a much improved description of the vapour-liquid equilibria and single-phase properties of associating fluids such as water, methanol, ammonia, hydrogen sulphide, and their mixtures. A comparison is also made between the theoretical predictions of the degree of association for water and the extent of hydrogen bonding obtained from molecular simulations of the SPC/E and TIP4P/2005 atomistic models.