[MMTK] Ewald sums.

Konrad Hinsen hinsen@cnrs-orleans.fr
Thu, 13 Sep 2001 12:27:31 +0200


> > For example, after loading python:
> > -----
> > >>> from MMTK import *
> > >>> universe = load("water.univ")
> > >>> universe.energy()
> > 1077872366.1194236
> > >>> from MMTK.ForceFields import Amber94ForceField
> > >>>universe.setForceField(Amber94ForceField(15.*Units.Ang,
> > 15.*Units.Ang))
> > >>> universe.energy()
> > -33920.758650668249
> 
> Can you print the result of universe.energyTerms() for both cases?
> This does look a bit strange, in general the energy with Ewald
> summation is not very much different from the value obtained with a
> sufficiently large cutoff.

A followup for the list: this problem turned out to be due to a
compiler sensitivity (strange expression, I know, but I am not yet
sure who is right on this issue) with gcc 2.96, the version that comes
with RedHat Linux 7.x. If you use this gcc version and use Ewald sums,
please upgrade to MMTK 2.2b7.

Konrad.
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