The SMx (x = 12, 8, or D) universal solvent models are implicit solvent models which using electronic structure calculations can compute solvation free energies at 298.15 K. While solvation free energy is an important thermophysical property, within the thermodynamic modeling of phase equilibrium, limiting (or infinite dilution) activity coefficients are preferred since they may be used to parameterize excess Gibbs free energy models to model phase equilibrium. Conveniently, the two quantities are related. Therefore the present study was performed to assess the ability to use the SMx universal solvent models to predict limiting activity coefficients. Two methods of calculating the limiting activity coefficient where compared: (1) the solvation free energy and self-solvation free energy were both predicted and (2) the self-solvation free energy was computed using readily available vapor pressure data. Overall the first method is preferred as it results in a cancellation of errors, specifically for the case in which water is a solute. The SM12 model was compared to both the Universal Quasichemical Functional-group Activity Coefficients (UNIFAC) and modified separation of cohesive energy density (MOSCED) models. MOSCED was the highest performer, yet had the smallest available compound inventory. UNIFAC and SM12 exhibited comparable performance. Therefore further exploration and research should be conducted into the viability of using the SMx models for phase equilibrium calculations.

中文翻译：

---

评估SM12，SM8和SMD溶剂化模型以预测298.15 K时的极限活度系数

SM x（x = 12、8或D）通用溶剂模型是隐式溶剂模型，使用电子结构计算可以计算298.15 K时的溶剂化自由能。虽然溶剂化自由能是重要的热物理性质，但在相热力学建模中平衡，极限（或无限稀释）活性系数是优选的，因为它们可用于参数化多余的吉布斯自由能模型以模拟相平衡。方便地，这两个数量是相关的。因此，本研究旨在评估使用SM x的能力通用溶剂模型可预测极限活度系数。比较了两种计算极限活度系数的方法：（1）预测了溶剂化自由能和自溶自由能，（2）使用容易获得的蒸气压数据计算了自溶自由能。总的来说，第一种方法是优选的，因为它可以消除误差，特别是对于水是溶质的情况。将SM12模型与通用拟化学官能团活度系数（UNIFAC）和内聚能密度修正模型（MOSCED）进行了比较。MOSCED是性能最高的产品，但可用化合物的库存最少。UNIFAC和SM12表现可比。用于相平衡计算的x模型。