Group contribution prediction of surface charge density profiles for COSMO-RS(OI)

A new method for predicting the surface charge density distribution (sigma profile) and cavity volume of molecules based on group contributions was developed. The original sigma profiles used for the regression were obtained using Gaussian 03 B3LYP/6311G(d,p). In total 1363 sigma profiles were used for the regression of group parameters. Group definitions are identical to those used previously for boiling point estimation. Original and estimated sigma profiles were used to predict activity coefficients at infinite dilution and VLE data of binary systems using the COSMO-RS(Ol) model. The results were compared with the experimental data stored in the Dortmund Data Bank. In many cases the results were of comparable accuracy. However, for a few compounds, poor results were obtained, in particular for conjugated components like nitrobenzenes. The method offers a fast and reliable generation of sigma profiles to be used with COSMO-RS(Ol) within its range of applicability. (c) 2007 American Institute of Chemical Engineers AIChE J, 53: 3231-3240, 2007.