Classical density functional theory for the prediction of the surface tension and interfacial properties of fluids mixtures of chain molecules based on the statistical associating fluid theory for potentials of variable range.
Classical density functional theory for the prediction of the surface tension and interfacial properties of fluids mixtures of chain molecules based on the statistical associating fluid theory for potentials of variable range.
复制标题
DOI：
10.1063/1.3449143
复制
发表时间：
2010-07
期刊：
影响因子：
--
通讯作者：
F. Llovell;A. Galindo;F. J. Blas;G. Jackson
中科院分区：
文献类型：
--
作者：
F. Llovell;A. Galindo;F. J. Blas;G. Jackson
本文采用密度泛函理论（DFT）中的变程吸引势统计缔合流体理论（SAFT-VR）。J. Gloor等人，J.Chem.Phys.121，12740（2004）]被重新审视并推广到处理混合物。Helmholtz自由能泛函是基于均匀流体的SAFT-VR方法，通过将自由能密度划分为参考项（包含所有短程相互作用并局部处理）和吸引力扰动（包含长程色散相互作用）来构建。在这项工作中，两个不同的泛函进行了比较。在第一，一个使用的平均场版本的理论来治疗的长程色散相互作用，通过引入一个短距离的吸引力的贡献，在参考项中的片段之间的吸引力的能量的相关性的效果的近似处理。在第二种方法中，按照Toxvaerd [S. Toxvaerd，J.Chem.Phys.64，2863（1976）]。SAFT-VR DFT形式主义，然后用于研究界面性质和吸附现象的界面。的表面张力和密度/组合物配置文件的混合物上的分子参数的影响进行了详细的分析，为不同的链长，链段直径，色散能，和吸引力范围的分子的二元混合物。的吸附现象的分子物种的不对称性的影响进行了研究在一定程度上深入。通过比较理论预测与一些真实的混合物的界面性质，证明了该方法的充分性。两个近似的自由能泛函的相对优点进行评估，通过检查选定的正构烷烃的混合物的汽液界面张力。该理论通常提供了一个很好的描述的混合物的界面性质，而不需要进一步调整的分子间参数，从检查的本体流体相行为单独。
The statistical associating fluid theory for attractive potentials of variable range (SAFT-VR) density functional theory (DFT) developed by [G. J. Gloor et al., J. Chem. Phys. 121, 12740 (2004)] is revisited and generalized to treat mixtures. The Helmholtz free-energy functional, which is based on the SAFT-VR approach for homogeneous fluids, is constructed by partitioning the free-energy density into a reference term (which incorporates all of the short-range interactions and is treated locally) and an attractive perturbation (which incorporates the long-range dispersion interactions). In this work, two different functionals are compared. In the first, one uses a mean-field version of the theory to treat the long-range dispersive interaction, incorporating an approximate treatment of the effect of the correlations on the attractive energy between the segments by introducing a short-range attractive contribution in the reference term. In the second, one approximates the correlation function of the molecular segments in the inhomogeneous system with that of a homogeneous system for an average density of the two positions, following the ideas proposed by Toxvaerd [S. Toxvaerd, J. Chem. Phys. 64, 2863 (1976)]. The SAFT-VR DFT formalism is then used to study interfacial properties and adsorption phenomena at the interface. A detailed analysis of the influence of the molecular parameters on the surface tension and density/composition profiles of the mixtures is undertaken for binary mixtures of molecules of different chain length, segment diameter, dispersive energy, and attractive range. The effect of the asymmetry of the molecular species on the adsorption phenomena is examined in some depth. The adequacy of the approach is demonstrated by comparing the theoretical predictions with the interfacial properties of some real mixtures. The relative merits of the two approximate free-energy functionals are assessed by examining the vapor-liquid interfacial tension of selected mixtures of n-alkanes. The theory generally provides an excellent description of the interfacial properties of the mixtures without the need for further adjustment of intermolecular parameters obtained from an examination of the bulk fluid-phase behavior alone.