Subject: Re: CCL:conformer population

From: "Dr. Andreas Klamt" <[email-masked]>
Date: Sat, 11 Nov 2000 14:51:44 +0100

Dear Bruce,

I am Andreas Klamt, the author of the solvation models COSMO and COSMO-RS. To my experience, the change in vibrational free
energies due to solvation is small, or at least it is usually a small contribution hidden within the non-electrostatic terms in
continuum solvation models. Thus it does not appear necessary to calculate frequencies in solution explicitely (which by the way
is not trivial). 

Within our COSMO-RS method (available as software COSMOtherm from COSMOlogic) we typically just calculate the total electronic
energy of the conformers in a conductor add the chemical potential of the conformer in a solvent (relative to conductor), as
calculated by COSMOtherm. Honestly spoken, we just forget about zero point vibrations a his place. 

This appears to work very well. In a recent blind-test on conformational free energies of polyionic cyclic amino-acids in water
COSMOtherm performed by far best. We had an rms of about 2.2 kJ/mol. Note, that this is for poly-ions. For neutral structures
there is goog hope to be even more accurate.

["Conformational analysis of cyclic acidic a-amino acids in aqueous solution - an evaluation of different continuum hydration
models."  Peter Aadal Nielsen, Per-Ola Norrby, Jerzy W. Jaroszewski, and Tommy Liljefors, manuscript, to be published]

Sincerely

Andreas

P.S.: We just got COSMOtherm running with Gaussian COSMO-calculations. The respective sub-release of Gaussian will be available
soon, hopefully.

--------------------------------------------------------------------------------
Dr. Andreas Klamt
COSMOlogic GmbH&CoKG
Burscheider Str. 515
51381 Leverkusen, Germany

Tel.: 49-2171-73168-1  Fax: ...-9
e-mail: [email-masked]
web:    www.cosmologic.de
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From: "Bruce. Tattershall" <[email-masked]>
Date: Fri, 17 Nov 2000 08:50:57 +0000 (GMT)

Thank you very much for your informative email.  Very few others have
replied, which I found quite surprising, considering how many people
must make use of this kind of calculation.

  Bruce