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