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.

Simple expressions are presented to determine if a binary system will exhibit a minimum or maximum boiling azeotrope using conventional free energy calculations using molecular simulation or electronic structure calculations in a continuum solvent. The expressions compare the solvation free energy of each component at infinite dilution relative to itself, requiring four total solvation free energy calculations per binary system. The solvation free energies can be related to intermolecular interactions and, therefore, shed insight into why an azeotrope occurs. The application of the expressions is demonstrated for 2366 binary systems using solvation free energies computed using electronic structure calculations in the SM12, SM8, and SMD universal solvent models. The overall success rate for predicting the correct phase behavior was 0.718, 0.711, and 0.685 for SM12, SM8, and SMD, respectively.

The SM<i>x</i> (<i>x</i>= 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 SM<i>x</i> 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 UNIFAC and MOSCED. 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 SM<i>x</i> models for phase equilibrium calculations.

The SM<i>x</i> (<i>x</i>= 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 SM<i>x</i> 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 UNIFAC and MOSCED. 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 SM<i>x</i> models for phase equilibrium calculations.

The SM<i>x</i> (<i>x</i>= 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 SM<i>x</i> 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 UNIFAC and MOSCED. 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 SM<i>x</i> models for phase equilibrium calculations.