CCL: MD of systems with a net charge using Ewald

 Sent to CCL by: Simon Halstead [joyjoyhappyjoy#%#yahoo.co.uk]
 By the energy I mean the energy of the isolated ion.
 My system has a single ion solvated in N SPC/E water.
 I obtain the energy of the isolate ion from the
 potential energy of the system minus the potential
 energy of N water (calculated separately). It is this
 energy of a single isolated ion that shows strong
 system size dependence.
 --- "Konrad Hinsen hinsen+/-cnrs-orleans.fr"
 <owner-chemistry]~[ccl.net> wrote:
 >
 > Sent to CCL by: "Konrad  Hinsen"
 > [hinsen#cnrs-orleans.fr]
 > On Oct 26, 2007, at 5:28, Simon Halstead
 > joyjoyhappyjoy * yahoo.co.uk wrote:
 >
 > > I am running MD simulations on systems with either
 > a net +1 or -1 charge using Ewald summation
 > > and dl_poly. The Ewald summation should correct
 > for the net charge by adding a smeared charge
 > > over the cell. However, my results show a serious
 > system size dependence for the potential energy
 > > (from the coulomb term).
 > > Does anyone know of any way to correct the energy
 > results?
 >
 > Ewald summation does indeed add a neutralizing
 > background charge density, which makes the
 > electrostatic energy finite. However, the energy
 > depends on the system size. If you think that in
 > your
 > specific case the energy should not depend on system
 > size, then please tell us why.
 > --
 >
 ---------------------------------------------------------------------
 > Konrad Hinsen
 > Centre de Biophysique Molculaire, CNRS Orlans
 > Synchrotron Soleil - Division Expriences
 > Saint Aubin - BP 48
 > 91192 Gif sur Yvette Cedex, France
 > Tel. +33-1 69 35 97 15
 > E-Mail: hinsen-.-cnrs-orleans.fr
 >
 ---------------------------------------------------------------------
 >
 >
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