Re: question on modifyAppliedForces()

From: Jim Phillips (
Date: Tue May 10 2011 - 21:31:42 CDT

Hi Brian,

This function just returns a reference to the applied forces list, to
which forces to be added to atoms are appended (I'm not at all proud of
this interface, but C++ was young back then). These forces are added to
the normal intermolecular forces; they do not replace them.

So, for your example, the resulting force is 1.0 + -2.0 = -1.0.


On Fri, 22 Apr 2011, Bennion, Brian wrote:

> Hello,
> I just want to do a sanity check about the use of modifyAppliedForce.
> In several sections of the namd2 code (globalmasterTMD, colvars, etc)
> this function seems to modify forces before use in calculations for the
> next timestep. Is this a modification that replaces the previously
> determined force or does it attenuate/potentiate the previously
> determined force? For example, if curForceX=1.00 and
> modifyAppliedForces() sends a force with an X term of myforceX=-2.0 is
> the resulting force that is used in the following steps equal to -1.0 or
> is it -2.0?
> Does that make anysense?
> Brian Bennion
> Biosciences and Biotechnology Division
> Lawrence Livermore National Laboratory
> 7000 East Ave Livermore California 94550
> phone:925-422-5722
> fax:925-424-4334

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