Mulliken Center for Theoretical Chemistry, Universität Bonn, Beringstr. 4, D-53115 Bonn, Germany.
J Chem Phys. 2017 Apr 21;146(15):154502. doi: 10.1063/1.4980032.
The quantum cluster equilibrium method is applied to model binary systems of molecular solvents. We minimize the computational effort as well as the experimental input and present the results obtained for the completely miscible acetonitrile/acetone, benzene/acetone, and water/acetone systems, as well as for the hardly miscible water/benzene system. Only clusters of sizes up to n = 3 are applied and these are optimized employing the low-cost functional PBEh-3c. The thermodynamic functions of the pure liquids are in reasonable agreement with experiments. For both non-water containing binary systems, the Gibbs energy of mixing can be reproduced with an accuracy of ≈0.25 kJ/mol. Water containing systems are not sufficiently described by small clusters. The empirical mean-field parameter a and exclusion volume scaling parameter b which depend on the experimental input are approximated by linear interpolation between their neat liquids' reference values. This makes the approach independent from the experimental data of the binary system. Despite the roughness of the approximation as well as the small size of the cluster sets, the approach is able to correctly predict the mixing behavior of all acetone systems. The benzene/water system is correctly predicted to be non-miscible at most mole fractions. A small range at high benzene concentrations (x> 0.8) is falsely predicted to be miscible.
量子团簇平衡方法被应用于模拟分子溶剂的二元体系。我们尽量减少计算工作量和实验投入，并呈现出完全互溶的乙腈/丙酮、苯/丙酮和水/丙酮体系，以及难溶的水/苯体系的结果。仅应用尺寸最大为 n = 3 的团簇，并使用低成本的泛函 PBEh-3c 对其进行优化。纯液体的热力学函数与实验值吻合良好。对于不含水的两个二元体系，混合吉布斯自由能可以以约 0.25 kJ/mol 的精度重现。对于含有水的体系，小团簇不能充分描述。经验性均方位移参数 a 和排斥体积标度参数 b 取决于实验输入，通过它们在纯液体参考值之间的线性插值进行近似，这使得该方法独立于二元体系的实验数据。尽管近似具有粗糙性，并且簇集的大小较小，但该方法能够正确预测所有丙酮体系的混合行为。苯/水体系被正确预测为在大多数摩尔分数下是不混溶的。在高苯浓度（x>0.8）时，一个小范围被错误地预测为是混溶的。
