From owner-chemistry@ccl.net Tue Jan  6 06:43:00 2009
From: "V ronique LEGRAND vflegrand(-)free.fr" <owner-chemistry,,server.ccl.net>
To: CCL
Subject: CCL:G: population inversion-resonance
Message-Id: <-38396-090106063758-28476-B3Uk0F94odfmehEVJdXY9g,,server.ccl.net>
X-Original-From: "V  ronique  LEGRAND" <vflegrand%%free.fr>
Date: Tue, 6 Jan 2009 06:37:55 -0500


Sent to CCL by: "V  ronique  LEGRAND" [vflegrand%%free.fr]
Dears CCLers,

I did an NBO calculation, and as my molecule is a radical I decided to test different basis set : UB3LYP 6-31G(d,p) and UB3LYP 6-311+G(d,p). With this large basis set, I have a warning message in the output :
 "Population inversion found on atom  N 1...."
I found many explication of CCL archive. They are all agree to tell that if their energy is only some kcal/mol It can be neglected.
My problem is, I have in an other part a very huge energy of delocalization between them. So I can't neglect them so easily.

The output seems to tell that the keyword "RESONANCE" might be use.
I found that this keyword is associated with NBO. But I found nowhere a description of this in the website of gaussian03.

Does-it exist ? And could it be really usefull for my problem? Or is there something better?

Thanks for your help.

LEGRAND Vronique


From owner-chemistry@ccl.net Tue Jan  6 14:19:01 2009
From: "Jim Kress ccl_nospam- -kressworks.com" <owner-chemistry{}server.ccl.net>
To: CCL
Subject: CCL: molecular mechanics and dynamics for metal-organic and organic-organic
Message-Id: <-38397-090106141713-7862-8jz0uwivPcI6bYvMDI+YOw{}server.ccl.net>
X-Original-From: "Jim Kress" <ccl_nospam*o*kressworks.com>
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Date: Tue, 6 Jan 2009 14:03:07 -0500
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Sent to CCL by: "Jim Kress" [ccl_nospam _ kressworks.com]
Try gromacs

http://www.gromacs.org/

There are other packages but this one meets your "free" requirement :>}

Jim 

> -----Original Message-----
> From: owner-chemistry+ccl_nospam==kressworks.com_-_ccl.net 
> [mailto:owner-chemistry+ccl_nospam==kressworks.com_-_ccl.net] 
> On Behalf Of Egbert Zojer egbert.zojer.:.tugraz.at
> Sent: Monday, January 05, 2009 11:11 AM
> To: Kress, Jim 
> Subject: CCL: molecular mechanics and dynamics for 
> metal-organic and organic-organic
> 
> 
> Sent to CCL by: "Egbert  Zojer" [egbert.zojer]_[tugraz.at] Dear all,
> 
> For the past few years, we have used density functional 
> theory to describe the properties of metal organic systems. 
> These include self-assembled monolayers on noble metals, or 
> strong organic acceptors and donors (experiencing significant 
> charge transfer when bonded to the metal surface)
> 
> As a complementary approach (bearing in mind all the 
> limitations of DFT, like the inability to describe dispersion 
> forces, which to our experience only partly overcome by 
> non-local functionals + to be able to describe much larger 
> and more complex systems), I would like to try out approaches 
> based on classical force fields (in particular MD). 
> Unfortunately, I know not much about such force fields apart 
> from their "general properties".
> 
> Therefore, I would be grateful about information on force 
> fields (+ suitable computar codes - if possible available 
> free of charge) with a proven track-record in
> * describing the interaction between conjugated organic molecules,
> * possibly also reasonably well parametrized to describe 
> interactions between organic molecules and noble (or not so 
> noble) metals in the absence of metal-organic charge transfer.
> * codes that would also allow to include charged species (if 
> necessary to be calculated on the DFT level.
> * info on shortcomings to be expected when applying such an 
> approach that a person with only a rudimentary understanding 
> of force fields might overlook.
> 
> Thanks a lot in advance,
> 
> Egbert
> 
> 
> 
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