Subject: AM1/NBO problem on G92.

From: "Guillem A. Sunyer" <[email-masked]>
Date: Tue, 16 Jul 1996 14:39:47 +0100

Dear Netters,

I am trying to perform a normal NBO analysis on an AM1 optimized
geometry by using Gaussian-92 package (that includes the G92NBO 3.1
code). The AM1 calculation runs nicely on G92. However, when I try to do
the NBO analysis with the following input:

%Mem=6000000
%Chk=int1b2-nbo
# AM1 SCF=DIRECT test Geom=Checkpoint Pop=NBORead Guess=Read
  Density=SCF

NBO calculation.

 0 1

$NBO RESONANCE $END

The program stops with the following NBO warning:
 
"An eigenvalue of the weighted PRE-NAO overlap matrix of -0.32692 has
been found, which is lower than the allowed threshold of 0.00000. This
is probably caused by either an error in the data given to the analysis
program or by numerical problems caused by near linear dependencies
among the basis functions."

All the NBO analysis that I have performed with several ab inito basis
set have been succesfully done. However, this problem always appears
when semiempirical AM1 & NBO analysis are done with G92.

Any help will be most welcome. 

Guillermo

PS Although this one should be the logical solution, I cannot run NBO
analysis on AMPAC 5.0 because our version does not handle NBO code...

-- 
Dr Guillermo A. Suner; Dep. de Quimica, UNIVERSITAT DE LES ILLES BALEARS
E-07071-Palma de Mallorca, SPAIN.
E-mail: [email-masked]    Tel: + 34 71 173498  Fax: + 34 71 173426 
WWW URL: http://www.uib.es/depart/dqu/dquo/suner.html