OZGE ENGIN wrote:
'The force is not the derivative of the potential', is it due to the types of calculations performed in PME, using of FFT for reciprocal sum? Because it does not matter while using reaction-field method.
Sorry, this phenomenon is a little complicated to me :)
this is only when you combine twin range (rcoulomb > rlist) and PME.
then the forces for a certain distance range are not computed at each
time step while the others are. you may want to (re)read the PME papers
and/or the gromacs manual about twin range.
Thanks for your attention!
Oz.
-----Original Message-----
From: David van der Spoel <[EMAIL PROTECTED]>
To: Discussion list for GROMACS users <gmx-users@gromacs.org>
Date: Sat, 01 Sep 2007 13:37:05 +0200
Subject: Re: [gmx-users] r_list and r_coulomb values while using PME
OZGE ENGIN wrote:
Hi all,
I can not understand why it is required to take same values for both r_list
and r_coulomb parameters when using PME for calculation of electrostatic
interactions?
I read archieve, and gromacs manual. In archieve, similar question had been
posted, but not replied yet.
Thanks in advance
if rlist < rcoulomb you will have a twin range interaction, meaning the
atom pair interactions for distance between these two will be computed
every nstlist steps only, while the interaction beyond rcoulomb will be
computed at each time step. this will lead to bad energy conservation,
since the force is not the derivative of the potential.
Oz.
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Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
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