CCL:G: COSMO, CPCM, and COSMO-RS definitions
- 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
--
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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
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