[lammps-users] how to obtain the interaction force in a set-forced group of atoms

Dear Steven,

I would like to simulate deformation process of nanowire during tensile/compressive loading. The model is quite simple that described as following. I have fixed several atomic layers in the ends of the wire to take as the loading tip by using fix setforce 0 0 0 command. Then, I apply the ramp velocity distribution to the whole wire to simulate the loading process. Here is the problem. During deformation the unfixed atoms will produce some amount of force on the loading tip (the fixed atoms in the ends). I would like to obtain the force that the loading tip is endured. However, since I use the fix setforce command to make an constrained condition, all the atomic force (fx, fy, fz) in the loading tip will be shown as Zero. Thus, I wonder how I can obtain the magnitude of force in the loading tip?
I have go through the Manual and found the compute group/group command can calculate the force between different groups of atoms. However, the command can only calculate the force due to the pairwise interaction. I am now using the EAM potential, so it seems not valid for my problem. Thus, is there any other ways to solve my problem, either using other command or modifying my model?

Best Regards,
Li Suzhi

Fix setforce stores the total force on the atoms it changes
before it does the change. These can be output, e.g.
with thermo output. See the doc page for fix setforce
for details.