Sigma-Profile Database for Using COSMO-Based Thermodynamic Methods

Abstract

Thermodynamic methods based on conductor-like screening models (COSMO) originated from the use of solvation thermodynamics and computational quantum mechanics. These methods rely on sigma profiles specific to each molecule. A sigma profile is the probability distribution of a molecular surface segment having a specific charge density. Two COSMO-based thermodynamic models are COSMO-RS (realistic solvation) developed by Klamt and his colleagues, and COSMO-SAC (segment activity coefficient) published by Lin and Sandler. Quantum mechanical calculations for generating the sigma profiles represent the most time-consuming and computationally expensive aspect of using COSMO-based methods. A growing number of scientists and engineers are interested in the COSMO-based thermodynamic models but are intimidated by the complexity of performing quantum mechanical calculations. This paper presents the first free, web-based sigma profile database of 1432 compounds. We describe the procedure for sigma profile generation, and we have validated our database by comparing COSMO-based predictions of activity coefficients, normal boiling point and solubility with experimental data and thermodynamic property database. We discuss improvements which include using supplemental geometry optimization software packages to provide good initial guesses for molecular conformations as a precursor to the COSMO calculation. Finally, this paper provides a FORTRAN program and a procedure to generate additional sigma profiles, as well as a FORTRAN program to generate binary phase-equilibrium predictions using the COSMO-SAC model. Our sigma profile database will facilitate predictions of thermodynamic properties and phase behaviors from COSMO-based thermodynamic models.

Prediction of vapor–liquid equilibrium for polymer solutions based on the COSMO‐SAC model

“…The screening charge density r à from the COSMO output is averaged to give the apparent charge r on a standard surface segment using the following equation 31 :…”

“…As the calculation of COSMO, different quantum chemistry software can be conveniently used for these systems. [17][18][19]31,32 In COSMO-SAC model, the most time-consuming processes are the optimization of molecular geometry. Currently, there are 1432 kinds of compounds that COSMO files have been provided.…”

“…Currently, there are 1432 kinds of compounds that COSMO files have been provided. 18,31,33 However, there is only a few of literature reported about the application of COSMO-types model in polymer systems. 34,35 The reason may be attributed to the fact that the polymer molecule is composed of thousands of monomers and the quantum mechanical calculation could not afford the arduous task using the existing computer equipment.…”

“…27 The specific parameters are cited from references 18,31 and the algorithm is the same as one in VT2005. 18,31,36 It is worthy to point out that the geometry optimization and COSMO calculation can also be calculated by using other quantum chemistry computation method such as PM6 semi-empirical methods 38 in MOPAC2009. 28 As a consequence, the COSMO files can be obtained to provide the optimized molecular geometry.…”

Enterprise Ionic Liquids Database (ILUAM) for Use in Aspen ONE Programs Suite with COSMO-Based Property Methods

“…This solution has been addressed by several research groups in different application fields and using rather dissimilar strategies 7,[12][13][14][15][16][17][18][19] . In particular, our group has been worked 20 in the integration of the molecular modeling and the process simulation via the COSMO-based 21,22 In the last five years, we have successfully applied COSMO-based/Aspen Plus (Aspen HYSYS) procedure to the design and analysis of new different processes using ILs: absorption of toluene in packed/tray columns 30 , absorption refrigeration cycles 31 , aromatic-aliphatic separation by liquidliquid extraction 25,32,33 , extractive distillation 34 and CO 2 capture by physical absorption 9 .…”