Subject: Imaginary freqs in Spartan (thanks, but...)

From: Victor Manuel "Rosas-Garc�a" <[email-masked]>
Date: Wed, 7 Apr 1999 08:11:37 -0700 (PDT)

Hello everybody,

About a couple of weeks ago I asked a question about getting rid of
imaginary frequencies in Spartan.  First I want to thank:

Stefan Fau
Ned Charles Haubein
Artem Masunov
Edmund Ndip

for their interest and suggestions.  I'm thinking that I was not
explicit enough regarding my problem, so here goes the situation:

I've been doing calculations of solvation energies using semiempirical
methods for about two years now.  At first, I used COSMO in MOPAC93,
and it was common to get "minima" with imaginary frequencies.  Within
MOPAC93, it was possible to tighten up some criteria, change the
optimization method, or (last resort) run an IRC to get rid of those
imaginary freqs.  It was painful but it usually worked (although in
some recalcitrant cases I was unable to eliminate all the imaginary
freqs).  Now I'm using the solvent models in Spartan and the problem
with "minima with imaginary freqs" has reappeared.  So my questions
are:

a) Is there a way to run an IRC within Spartan?

b) Are solvent models bound to produce spurious imaginary frequencies?
if so, why?

Thanx

Victor

===
Victor M. Rosas García
Computational Chemistry Apprentice

e-mail: [email-masked]

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