Subject: Re: CCL:problems with Gaussian 03, model CPCM

From: Andreas Klamt <klamt <> cosmologic.de>
Date: Sat, 19 Mar 2005 06:21:10 +0100

Amelia,

we have done several hundreds of amiacids and oligopeptides in water 
with DFT/COSMO in TURBOMOLE. Apart from the big conformational 
flexibility, there were no problems in the optimization at all. 
Unfortunately we do not have efficient COSMO frequency calculations in 
TURBOMOLE yet, but let me ask what you need them for. In some way 
continuum solvation models appear to include the change in vibrational 
free energy by solvation implicitly. So when you calculate the 
vibrational contributions in the gas phase for the corresponding 
conformations, you will have all you need for thermochemistry. If you 
should really want to go into frequencies in solutions, be aware that 
2nd derivatives of the total energy are not the same as frequencies in 
solution, due to the non-equilibrium solvation problem, which will 
hinder the rotational degrees of polarization to follow the highe 
frequency vibrations of the solute instantaneously. So you enter a very 
complicated area if you decide to do so.

Regards

Andreas
(father of COSMO)

-- 
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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
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amvaldez <> uach.mx wrote:

>To whom it may concern:
>I am working in Centro de Investigacion en Materiales Avanzados de 
>Chihuahua, Mexico.
>I am working with Gaussian 03, and  I have tried to calculate 
>optimization, frequency and energy, in water solution, using CPCM 
>model, DFT, basis set 3-21 G, for some aminoacids and tripeptides, but 
>all procesing have aborted, because some bonds disapear and they form 
>hidrogen bonds. In all cases, a legend appears, saying that a hidrogen 
>has two bonds.
> I think I could try another model, but I'd like you to sugest me the 
>best for water solution, for DFT.  
>I'll thank you for your kindly attention.
>       Sincerely:
>       Amelia Valdez Aguirre  
>
>
>
>
>
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