Correspondence pubs.acs.org/IECR
Comment on “An Improvement to COSMO-SAC for Predicting Thermodynamic Properties” Andreas Klamt†,‡ †
COSMOlogic GmbH & Co. KG, Leverkusen, Germany Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg, Germany
‡
(7) Lin, S. T.; Sandler, S. I. Reply to “Comments on ‘A Priori Phase Equilibrium Prediction from a Segment Contribution Solvation Model’”. Ind. Eng. Chem. Res. 2002, 41, 2332−2334.
X
iong, Sandler, and Burnett presented, in their article,1 some new parametrization of the COSMO-RS 2,3 reimplementation COSMO-SAC,4 based on two different quantum chemical codes used for the generation of the COSMO files. In eq 4, they reported the “COSMO-SAC” equation for the σ-averaging, which had been introduced in an erratum5 in 2004, and which differs from the original COSMORS and COSMO-SAC averaging equation2,4 by a scaling factor fdecay in the Gaussian weight. In eq 12 of their latest article,1 they now offer the original averaging equation as a “simplification of eq 4”. The authors are now using quite exactly the averaging radii of 0.82 Å consistent with their first COSMO-SAC paper with DMol3 and of 0.51 Å, i.e., almost exactly the averaging radius suggested in the original COSMO-RS paper with COSMO files from ADF. The authors’ values are such that rav ≪ reff. Hence, it should be clearly stated: In contrast to the explicit claim made in the original COSMO-SAC paper4 of having achieved a consistency of rav and reff, all COSMO-RS implementations, including COSMO-SAC, do require an averaging radius rav, which is much less than radius reff of an effective contact area. The interested reader is referred to earlier comments regarding this issue.6,7
■
AUTHOR INFORMATION
Notes
The author declares the following competing financial interest(s): The author declares to be the inventor of the COSMO-RS method and to develop and distribute COSMORS in the form of the COSMOtherm software commercially via his company, COSMOlogic.
■
REFERENCES
(1) Xiong, R.; Sandler, S. I.; Burnett, R. I. An Improvement to COSMO-SAC for Predicting Thermodynamic Properties. Ind. Eng. Chem. Res. 2014, DOI: 10.1021/ie404410v. (2) Klamt, A. Conductor-Like Screening Model for Real SolventsA New Approach to the Quantitative Calculation of Solvation Phenomena. J. Phys. Chem. 1995, 99, 2224. (3) Klamt, A.; Jonas, V.; Bürger, T.; Lohrenz, J. C. W. Refinement and Parametrization of COSMO-RS. J. Phys. Chem. A 1998, 102, 5074. (4) Lin, S. T.; Sandler, S. I. A Priori Phase Equilibrium Prediction from a Segment Contribution Solvation Model. Ind. Eng. Chem. Res. 2002, 41, 899−913. (5) Lin, S. T.; Sandler, S. I. A Priori Phase Equilibrium Prediction from a Segment Contribution Solvation Model [Erratum]. Ind. Eng. Chem. Res. 2004, 43 (5), 1322. (6) Klamt, A. Comments on “A Priori Phase Equilibrium Prediction from a Segment Contribution Solvation Model”. Ind. Eng. Chem. Res. 2002, 41, 2330−2331. © 2014 American Chemical Society
Published: May 15, 2014 8935
dx.doi.org/10.1021/ie501545c | Ind. Eng. Chem. Res. 2014, 53, 8935−8935
