Subject: Mopac93: Structure of excited states

From: <[email-masked]>
Date: Wed, 3 Jul 1996 17:07:39 +0200

I am interested in the relative energies and structures of the first excited
states (triplet and singlet) of a series of compounds.  I have obtained the
energies relative to the ground state using the keywords: MECI C.I.=2.

I now want to refine the structures of these states, but after 10 cpu-hr on an
Indigo2, the gradients are still very large (> 20) and appear to be oscillating.
I started the calculation with the optimized ground state structure, and used
the keywords: AM1 EF MECI C.I.=2 ROOT=2 (for the triplet, ROOT=3 for the
singlet).  I have also done the calculation adding SHIFT=15, in an attempt to
damp the oscillation.

This is my first attempt at working with excited state structures. . .is this
typical behavior, and I just need to be patient (sigh!), or have I missed
something?

If there is interest, I will summarize useful replies, for which I thank the
authors in advance.

===========================================================================
  Stephen B. Bowlus, Ph.D.                Computer-Aided Molecular Design
                                          Research Division
  e-mail: [email-masked]               Sandoz Agro, Inc.
  Phone:  + 1 415 354 3904                975 California Ave.
  Fax:    + 1 415 857 1125                Palo Alto, CA 94304
===========================================================================