TclBC forces on individual atoms

From: Udaya Dahal (
Date: Sun Mar 31 2019 - 10:24:52 CDT

Hi Everyone,

I used TclBC forces to restrict ions to certain regions of a periodic box.
Everything works exactly as it is supposed to work. One of the problem I
face is the transition of ions from one region to the other, which I have
to wait until next step to map it back using TclBC forces and this makes
uneven charge distribution in those regions. Also, I wonder how the force
on individual atoms are applied (for. eg. addforce "0 0 5"). It seems to me
that we are applying force randomly to ions that transit from one region to
another to map back it to its original location and may give rise to
artifact (in an otherwise an equilibrium simulation) due to random forces.
Instead I would like to use a wall to have a smooth potential function to
restrict ions to the certain region like half parabola. I am wondering if
it is possible to add such potential at the point of interest and for
specific atoms only. If so, how can we implement this?

I appreciate your help !

Udaya Dahal

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