Zhao Honggang, McCabe Clare
Department of Chemical Engineering, Vanderbilt University, Nashville, TN 37235, USA.
J Chem Phys. 2006 Sep 14;125(10):104504. doi: 10.1063/1.2337624.
A statistical associating fluid theory for potentials of variable range to model dipolar fluids is presented. The new theory, termed the SAFT-VR+D equation (the statistical associating fluid theory for potentials of variable range plus dipole), explicitly accounts for dipolar interactions and their effect on the structure of the fluid. This is achieved through the use of the generalized mean spherical approximation (GMSA) to describe a reference fluid of dipolar square-well segments. Isothermal-isobaric and Gibbs ensemble Monte Carlo simulations have been performed in order to test the new theoretical approach. Predictions for the thermodynamic properties and phase behavior of dipolar square-well monomer and chain fluids, in which one or more segments are dipolar, are considered and compared with new computer simulation data. The results show that the equation of state in general provides a good description of the phase behavior of dipolar monomer and chain fluids. Some deviations are seen between the simulation data and theoretical predictions for monomer fluids with large dipole moments and for molecules composed of segments with dipoles in different orientations. This is addressed through the replacement of the GMSA by the linearized exponential approximation.
提出了一种用于可变范围势的统计缔合流体理论，以对偶极流体进行建模。新理论称为SAFT-VR+D方程（可变范围势加偶极的统计缔合流体理论），明确考虑了偶极相互作用及其对流体结构的影响。这是通过使用广义平均球近似（GMSA）来描述偶极方阱段的参考流体来实现的。为了测试新的理论方法，进行了等温等压和吉布斯系综蒙特卡罗模拟。考虑了偶极方阱单体和链状流体（其中一个或多个段是偶极的）的热力学性质和相行为的预测，并与新的计算机模拟数据进行了比较。结果表明，状态方程总体上能很好地描述偶极单体和链状流体的相行为。对于具有大偶极矩的单体流体以及由具有不同取向偶极的段组成的分子，模拟数据与理论预测之间存在一些偏差。通过用线性化指数近似代替GMSA来解决这一问题。
