Hi Dan,
Preliminary tests would seem to indicate that qm_ewald=2 can lead to poor
energy conservation, although not nearly as bad as you would get from
having a small or discontinuous cutoff (i.e. without qmmm_switch = 1). In
fact the energy drift was usually the opposite with energy "leaving" the
system rather than the energy going up. However, I should point out that
these were relatively long (0.5 ns) NVE simulations; any kind of
thermostatting might substantially reduce any artifacts (although perhaps
that is not a good thing).
Again, these are preliminary results and we are still verifying them (box
size and shape dependence, etc). The main AMBER QM/MM developers will be
putting these results out in a paper soon (in preparation).
Regards,
Brian
On Fri, Jul 13, 2012 at 12:01 PM, <DJH71.pitt.edu> wrote:
> Hi all,
>
> I'm running QM/MM simulations on Amber12 using PM6 theory and I've
> frequently been receiving SCF Convergence errors ('Unable to achieve self
> consistency to the tolerances specified. No convergence in SCF after 1000
> steps...'). By experimenting with various settings, I found that setting,
> qm_ewald = 2, seems to solve the problem. The Amber11 manual says that
> this setting has not been extensively testing and I was wondering if
> anyone could offer me informations about how it may affect the dynamics of
> my simulations, or if anyone has encountered a similar problem/solution.
> Thanks!
>
> Dan Hatfield
>
>
>
>
> _______________________________________________
> AMBER mailing list
> AMBER.ambermd.org
> http://lists.ambermd.org/mailman/listinfo/amber
>
--
================================ Current Address =======================
Brian Radak : BioMaPS
Institute for Quantitative Biology
PhD candidate - York Research Group : Rutgers, The State
University of New Jersey
University of Minnesota - Twin Cities : Center for Integrative
Proteomics Room 308
Graduate Program in Chemical Physics : 174 Frelinghuysen Road,
Department of Chemistry : Piscataway, NJ
08854-8066
radak004.umn.edu :
radakb.biomaps.rutgers.edu
====================================================================
Sorry for the multiple e-mail addresses, just use the institute appropriate
address.
_______________________________________________
AMBER mailing list
AMBER.ambermd.org
http://lists.ambermd.org/mailman/listinfo/amber
Received on Fri Jul 13 2012 - 09:30:03 PDT
