Quantumchemical (COSMO-RS-Type) Models
After the great success of COSMO-RS (A. Klamt, COSMOLogic), similar models were developed by various research groups.
The DDB software contains implementations of COSMO-RS(Ol) and COSMO-SAC that can be used for the estimation of different types of phase equilibria and excess properties.
COSMO-RS and similar models derive the residual contribution to the activity coefficient from shielding charge density missfit interactions between contacting surface segments of the molecules. The different shielding charge densities are depicted by different colors for cyclohexane and nitromethane in the picture on the right. Instead of bringing the 3-dimensional representations of the molecules into contact, COSMO-RS models assume that the probability of contact of two surface segments is only governed by the size of energy missfit. This greatly simplifies the calculation as only the shielding charge density distribution (s-profile) has to be considered.
The required s-profiles were derived using the program package Gaussian using the B3LYP DFT functional and the 6-311G(d,p) basis set and are delivered as a separate databank (s-Profile Data Bank).
Quantumchemical calculations are especially tedious in case of large molecules. To provide a reliable alternative, the program package Predict Pure allows to estimate the required s-profiles via group contribution.
|2009||Group Contribution Prediction of Surface Charge Density Distribution of Molecules for COSMO-SAC||Mu T., Rarey J., Gmehling J.||Journal||AIChE J., 55, 12, 3298 3300 (2009)|
|2009||Application of COSMO-RS Type Models to the Prediction of Excess Enthalpies||Constantinescu D., Rarey J., Gmehling J.||Journal||Ind.Eng.Chem.Res., 277, 1,8710-8725 (2009)|
|2008||Reply to: Comments on Performance of COSMO-RS with Sigma Profiles from Different Model Chemistries||Mu T., Rarey J., Gmehling||Journal||Ind.Eng.Chem.Res., 47, 3, 989 989 (2008)|
|2008||Conductor-Like Screening Model for Real Solvents ( COSMO-RS)||Mu T., Gmehling J.||Journal||Huaxue-jinzhan, 20, 10, 1487 1494 (2008)|
|2007||Performance of COSMO-RS with Sigma Profiles from Different Model Chemistries||Mu T., Rarey J., Gmehling J.||Journal||Ind.Eng.Chem.Res., 46, 20, 6612 6629 (2007)|
|2007||Group Contribution Prediction of Surface Charge Density Profiles for COSMO-RS(Ol)||Mu T., Rarey J., Gmehling J.||Journal||AIChE J., 53, 12, 3231 3240 (2007)|
|2005||Weiterentwicklung thermodynamischer Vorhersagemodelle durch Einsatz von quantenchemischen Methoden||Grensemann H.||PhD thesis||Thesis, Carl-von-Ossietzky-Universität Oldenburg, 1-235, 2005|
|2005||Rebuttal to the Comments of Andreas Klamt on "Performance of a COSMO-RS Model in Comparison to Classical Group Contribution Methods"||Grensemann H., Gmehling J.||Journal||Ind.Eng.Chem.Res., 44, 17, 7043 7044 (2005)|
|2005||Systems with Ionic Liquids: Measurement of VLE and gamma-infinite Data and Prediction of their Thermodynamic Behavior using Original UNIFAC, mod. UNIFAC(Do) and COSMO-RS(Ol)||Kato R., Gmehling J.||Journal||J.Chem.Thermodyn., 37, 6, 603 619 (2005)|
|2005||Performance of a Conductor-Like Screening Model for Real Solvents Model in Comparison to Classical Group Contribution Methods||Grensemann H., Gmehling J.||Journal||Ind.Eng.Chem.Res., 44, 5, 1610 1624 (2005)|
Sigma-Profiles for COSMO-RS Type Models
For the use with COSMO-RS type models like e.g. COSMO-RS, COSMO-SAC and COSMO-RS(Ol), a large data bank with the required sigma profiles has been prepared. As the quantumchemical calculations become very demanding for large molecules, group contribution methods have been developed to predict sigma profiles. These complimentary methods are delivered with Predict Pure and lead to reliable results for not too complex or multifunctional structures.
Sigma profiles from DDB-Sigma can be used within the DDB software (DDB Mixture Predict Add-On) and in most third party software (in COSMOTherm® a specially optimized parametrization for these profiles is available).