Hi,
Late reply: the main problem with the system that you use is that with a
total charge of -1, you have a molecule with one part being -2 charged
(the two carboxylic groups) while the other part is charged +1. In gas
phase, the electrostatic interaction is so large that your molecule
bends and, at some point of the minimization, you have convergence
problems because, when the two charged groups are close, there are some
electron flows that the SCF converger can't handle (may be due to some
degeneracies of the wavefunctions). If, for example, you use qmcharge=-3
instead of qmcharge=-1, the optimization works "correctly" (but it's a
different chemistry of course) because of the repulsive -2 and -1
molecular groups.
As suggested by Jason, you should use some continuum model to
counter-balance the strong intermolecular electrostatic interactions,
but this is not available in sqm afaik. Another way would be to use
counterions to interact with your charged groups. That should do the trick.
Gerald.
On 05/08/2014 12:16 PM, Hannes Loeffler wrote:
> Hi,
>
> I can't get the attached structure (sqm.in) converged. What happens is
> that the wave function won't converge somewhere along geometry
> optimisation, at some arbitrary step (not the first step) depending on
> name list parameters.
>
> I have no particular interest in this one. The problem just came up in
> a larger test set. The structure is ZINC03814828. Same result with
> ZINC03814832 which is almost the same.
>
> The current name list is an outcome of playing around with various
> parameters but without luck. What I wonder is if this could still be
> made to converge or if there is a set of known structures which just
> cannot be converged? If I replace the carboxy-ethyl group with propyl
> the structure converges at scfconv=1.0D-9.
>
> Many thanks,
> Hannes.
>
>
>
>
> _______________________________________________
> AMBER mailing list
> AMBER.ambermd.org
> http://lists.ambermd.org/mailman/listinfo/amber
>
--
____________________________________________________________________________
Prof. Gerald MONARD
SRSMC, Université de Lorraine, CNRS
Boulevard des Aiguillettes B.P. 70239
F-54506 Vandoeuvre-les-Nancy, FRANCE
e-mail : Gerald.Monard.univ-lorraine.fr
tel. : +33 (0)383.684.381
fax : +33 (0)383.684.371
web : http://www.monard.info
____________________________________________________________________________
_______________________________________________
AMBER mailing list
AMBER.ambermd.org
http://lists.ambermd.org/mailman/listinfo/amber
Received on Tue May 20 2014 - 08:00:03 PDT
