- From: Ödön Farkas <farkas * chem.elte.hu>
- Subject: CCL:G: Constraints?
- Date: Thu, 27 Nov 2008 09:11:17 +0100
Sent to CCL by: =?ISO-8859-1?Q?=D6d=F6n?= Farkas [farkas]_[chem.elte.hu]
It is not really possible to say what to do in general in a case like
yours. Many kind of problems may occur, like the bonding of the stacked
molecules. To try to solve this choose two proper atoms (A1 and A2) in
the two molecules and add
A1 A2 B
to get proper bonding between the stacked molecules. You might freeze
the bond angles defined for this bond then.
If zou have more choices to connect stacked molecules you might add all
of them. Of course, this will just help the description of the motions
of atoms with redundant internals and should not affect the result.
If you have further questions contact me directly.
On Mon, 2008-11-24 at 08:28 -0500, David Close closed[*]etsu.edu wrote:
> Sent to CCL by: "David Close" [closed(~)etsu.edu]
> I'm having a problem imposing constraints on a series of stacked
molecules. I'm trying to look at the influence of neighbors in a problem
involving a crystal structure. When I get up to three molecules in a stack the
middle molecule tends to move away from the stack. I need to impose
constraints, but I keep getting a message "Curvilinear step not converged.
Error in constraints". Thuis is in GAussian. On another system the
program seems to fuss about symmetry?
> My questions is, what calculations are being performed to decided whether
or not a constraint is suitable? If one knows what calculations were being
perfomred, is it possible to add suitable constraints? It seems as if a few bond
constraints work, but when I add constrained angles, the curvilinear message
appears after 100 "tries".>
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