*From*: Andreas Klamt <klamt**cosmologic.de>*Subject*: CCL:G: COSMO, CPCM, and COSMO-RS definitions*Date*: Tue, 21 Feb 2006 09:09:59 +0100

Sent to CCL by: Andreas Klamt [klamt() cosmologic.de] Dear CCLers, this morning I again got quite angry about two papers mixing up the term COSMO, CPCM, and COSMO-RS, and therefore I like to explain them here shortly again. Please try to use them correctly and cite them correctly, when you write your papers using one of these methods. - COSMO: The conductor-like screening model is the variant of the continuum solvation models, which uses a scaled conductor boundary condition instead of the much more complicated dielectric boundary condition for the calculation of the polarization charges of a molecule in a continuum. The correct reference is [A. Klamt, G. Schüürmann, J. Chem. Soc. Perkin Trans.2 (1993) 799] COSMO has turned out to be computationally extremely efficient and robust, and to be less sensitive to outlying charge error. Therefore it has been implemented in in a wide range of quantum chemical codes. Please note that there are differences - mainly regarding the cavity construction and the radii defaults - in the various implementation, and specially between the implementations originating from my code and those originating from PCM or other codes. Nevertheless, I think all of them should be summarized under the expression COSMO. (It is important to note, that COSMO means a scaled conductor boundary condition, not a conductor itself, as often written in literature. It is not a conductor model, but a conductor-like model!) - CPCM is the implementation of COSMO in the PCM framework (V. Barone and M. Cossi, J. Phys. Chem. A 1998, 112, 1995ff), as most widely distributed and used in the Gaussian program. To be honest, I would be grateful if a citation to the original COSMO paper would be given as well when using CPCM or another re-implementation, because meanwhile 60% of the COSMO usages do not refer to COSMO anymore. - COSMO-RS (COSMO for real solvents, [1,2]) is a statistical thermodynamics post-processing of COSMO calculations, which I personally consider as the most physically sound continuum solvation model presently availably. It extends the applicability of quantum chemistry to the entire range of fluid phase thermodynamics, including mixtures and variable temperatures. COSMO-RS is based on COSMO calculations (COSMO files) for the individual solutes and solvents). COSMO-RS calculations require a COSMO-RS post-processing program, e.g. our COSMOtherm program. (Just for curiosity: I - as the inventor of COSMO - do not believe in the simple dielectric continuum solvation models at all, neither PCM nor COSMO. I am convinced that only by the RS extension a reasonable physics is put into these models. Therefore you will not find a single quantitative COSMO parameterization by me. Since 1994 I only work on COSMO-RS) 1. [1] A. Klamt, J. Phys. Chem. 99 (1995) 2224 2. [2] A. Klamt, V. Jonas, T. Buerger, J.C.W. Lohrenz, J. Phys. Chem. 102 (1998) 5074-5085 - Since Gaussian03 there is (or there was - I am not absolutely sure about the latest sub-releases) a keyword COSMORS available in PCM. This keyword has caused a lot of misuse. It was intended to trigger the right settings in PCM in order to produce COSMO files that can be used in COSMOtherm. But now many Gaussian users use this keyword and report the results as COSMO-RS calculations. This is absolutely wrong!!! These are CPCM calculations using the defaults optimized within COSMO-RS. By the way, even the term "KLAMT radii" has entered literature, since Gaussian introduced the keyword "radii=KLAMT". I am not a fan of such personalization. Please use the expression "radii optimized for COSMO-RS" or "COSMO-RS radii" and use reference [2] for these radii. Thanks for your help in avoiding more confusion Andreas Klamt P.S.: A rather complete description of COSMO and COSMO-RS is given in my recent book "COSMO-RS: From Quantum Chemistry to Fluid Phase Thermodynamcs and Drug Design", Elsevier, 2005 -- ----------------------------------------------------------------------------- Dr. habil. Andreas Klamt COSMOlogic GmbH&CoKG Burscheider Str. 515 51381 Leverkusen, Germany Tel.: +49-2171-73168-1 Fax: +49-2171-73168-9 e-mail: klamt=cosmologic.de web: www.cosmologic.de ----------------------------------------------------------------------------- COSMOlogic Your Competent Partner for Computational Chemistry and Fluid Thermodynamics -----------------------------------------------------------------------------