addforce for ReaxFF simulation

Dear all,

I face a problem to apply a specific force to a system (Al2O3) described by ReaxFF potential.
The purpose is to move a fixed region with constant shear stress (=force/area).

I write the following commands in the script:

fix 3 upper setforce 0.0 0.0 0.0
fix 4 upper aveforce 1.0 0.0 0.0

It does work well for a simple system, Cu by EAM.
However, when I apply it to Al2O3, the region where I apply force never moves.

Any one has some ideas?

Thank you.

Yunjiang Wang

What units were used for EAM and ReaxFF? Were the “1.0” changed accordingly for different unit systems?

Ray