From: Kamp, Marc vander (Marc.vanderKamp_at_wur.nl)
Date: Wed Aug 25 2004 - 01:29:18 CDT
Dear Jim and others,
I'm currently using the pair interaction function in NAMD. Is my understanding of the bug-description ( <http://www.ks.uiuc.edu/Research/namd/wiki/index.cgi?NamdKnownBugs> http://www.ks.uiuc.edu/Research/namd/wiki/index.cgi?NamdKnownBugs <http://www.ks.uiuc.edu/Research/namd/wiki/index.cgi?NamdKnownBugs) correct> ) correct? I read it as follows: although the individual forces that are output from pair interaction calculation are incorrect (x, y, z for vdW and electrostatic forces), upon addition of all 6 forces the correct interaction-energy is obtained?
I hope so, otherwise some results are suddenly meaningless.....
From: owner-namd-l_at_ks.uiuc.edu on behalf of Jim Phillips
Sent: Tue 24-8-2004 18:06
To: Jérôme Hénin
Subject: Re: namd-l: Direction of the force in Pair interactions
Yes. It's a bug. The NAMD 2.5 interaction force output is just wrong.
On Tue, 24 Aug 2004, [iso-8859-1] Jérôme Hénin wrote:
> Hi all,
> In the NAMD manual, the section about pair interaction calculations reads "
> The displayed force is the force on atoms in group 1". I expect the force
> exerted on group 1 to be the opposite of the one exerted on group 2.
> However, when I swap the group flags, I obtain exactly the same force vectors,
> not the opposite.
> Has anyone got an explanation for this?
> Jérôme Hénin
> Equipe Dynamique des Assemblages Membranaires
> Université Henri Poincaré / CNRS UMR 7565
> B.P. 239 54506 Vandoeuvre-lès-Nancy Cedex
> Tel : (33) 3 83 68 43 95 Fax : (33) 3 83 68 43 71
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