Subject: SCF convergence criteria

From: "Noel O'Boyle" <noel.oboyle2^at^mail.dcu.ie>
Date: Wed, 3 Sep 2003 17:48:29 +0100

Hello all,
This is a Gaussian 03 question.

Does anybody know or understand why the default SCF convergence criteria
for single point calculations is looser than the default for geometry optimisations?

I would have expected them either to be the same for both (for consistency)
or the opposite way around (since you can afford to spend more time on a
single point convergence).

In short, if you geometry optimise a structure, surely you should use SCF=Tight
if you do a subsequent single point energy calculation. (Of course, you
can avoid this question if you use Guess=Read.)

Thanks,
Noel O'Boyle