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From: Mr Andrew D Allen <chp1aa "-at-" surrey.ac.uk>
Message-Id: <9404111310.AA24031#* at *#central.surrey.ac.uk>
Subject: CCL:Problem with SCF convergence in AMPAC
To: chemistry: at :ccl.net
Date: Mon, 11 Apr 94 14:10:23 BST
Mailer: Elm [revision: 70.85]



I am running AMPAC v2.1 and have run into problems with SCF convergence. I have
a large, ~60 atoms, molecule which converges OK if carry out a geometry
optimisation on all coordinates. The problem arises when I try to constrain the
optimisation by flaging some of the bonds, angle and torsions to not be
optimised.

        Has anyone experienced this problem with Semi-emp, or QM methods in
general, and has anyone any possible ways to overcome the problem. I would like
to avoid doing a full geometry optimisation for the molecule due to its size.

Andy.

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