Benchmarking Different QM Levels for Usage with COSMO-RS

The COSMO-RS method is an established method for the prediction of fluid phase properties such as activity coefficients, liquid–liquid equilibria, and free energy of solvation. It is also frequently used in quantum chemistry-based chemical reaction modeling to predict the solvation contribution to the reactions. The COSMOtherm software, which features the currently most advanced implementation of COSMO-RS, is based on quantum chemical COSMO calculations using the BP functional with the def2-TZVPD basis set. As the accuracy of COSMO-RS depends on the accuracy of the underlying quantum chemical (QC) calculation, it is important to validate the currently used level against other common, presumably superior, approaches such as the more recently developed M06-2x hybrid density functional or wave function methods such as MP2. As compared to other applications where the electronic energy is the most important result of the QC calculation, the COSMO-RS method has a much higher dependence on the molecular polarity...