Subject: Re: CCL:Optimization in transition state

From: Olalla Nieto Faza <faza.-at-.uvigo.es>
Date: Tue, 26 Oct 2004 17:26:05 -0500

Just try to use  "opt=(ts,noeigen, modredundant)"
in your command line. 
What is happening is that the optimization algorithm checks the
curvature of the hessian at each step, and tells the program to die if 
the number of negative eigenvalues is not the expected (one, in this
case). When you use this keyword, the program will continue the
optimization even if it finds no negative eigenvalue or more than one.

In the gaussian manual (have a look at
http://www.gaussian.com/g_ur/k_opt.htm ) they say it is not advisable to
disregard this test, but I have been successfully using the "noeigen"
keyword by default in my ts optimizations for quite a while (otherwise,
unless you have very good initial guesses, you are often going to find
this error message and see your calculations die in the first
optimization steps).

Regards,

Olalla

On Tue, 2004-10-26 at 10:19, Arvydas Tamulis wrote:
> Dear Colleagues,
> 
> Would you please to help me because received unexpected stop during 
> optimization in transition state of biological derivatives applying Gaussian03.
> The input line is follows:
> 
> #P B3LYP 6-31G Opt=(TS,ModRedundant) IOp(6/3=12) DIIS SCFCYC=120
> 
> The optimization started, but after one cycle stopped:
> 
> Optimization stopped.
>      -- Wrong number of Negative eigenvalues: Desired=  1 Actual=  0
>      -- Flag reset to prevent archiving.
> 
> My question is: what does it means these comments in G03 and how to avoid 
> this stopping?
> 
> Best regards, Arvydas Tamulis
> 
> 
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-- 

________________________________________________________________________________
Olalla Nieto Faza                              Ph: (+34) 986-813721
Graduate Student                               e-mail: faza.-at-.uvigo.es 
Dpto. Quimica Organica                         http://webs.uvigo.es/faza
Universidade de Vigo                           
Lagoas-Marcosende 36200
Vigo (Spain)