Subject: geometry optimization methods

From: Dale Andrew Braden <[email-masked]>
Date: Mon, 7 Apr 1997 16:16:31 -0700 (PDT)

Dear CCL,

A brief question:  Are there any circumstances in which a geometry
optimization in Cartesian coordinates would be *faster* than in redundant
internal coordinates?

The reason I am asking is because I am trying to optimize the geometry of
a hydrogen-bonded dimer in a solvent medium using Gaussian 94, and the
change in the two intermolecular Z-matrix coordinates (distance and angle)
remains large for many, many iterations.  The geometry isn't exactly
oscillating between two structures, but it isn't settling down, either,
and I thought that perhaps by changing the optimization method from
redundant internal coordinates (the default method in G94) to cartesians,
the optimization might proceed more smoothly to a converged minimum.  I
don't want to try this unless it can work, because the calculation is
expensive.

Best wishes to all,

Dale Braden
Department of Chemistry
University of Oregon
Eugene, OR 97403-1253
[email-masked]