Using TCLforces to rescale force(s) on particular atom(s) --- loadtotalforces, addforce and previous/current timestep issue

From: Gungor Ozer (
Date: Thu Jan 19 2012 - 11:44:29 CST

Dear all,

I have been trying to adapt a TCL script that would use TCLforces to
rescale force on specified atoms. The idea is simple:

1) Calculate current force on a particular atom, f ---
2) Rescale it using some factor, x.
3) Add force, (x-1)*f --- (addforce)

I was planning to do this using the built-in loadtotalforces and addforce
commands. However, there is one issue: loadtotalforces reads the total
forces on each requested atom in the "previous timestep" but addforce adds
the force at the "current time step".

Is there anyway to get around this? Any input will be helpful and greatly

Thanks in advance,

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