[lammps-users] Question about fix move

Hi: I am using the command fix move to rotate a group of atoms. Is
there any way that I can get the total force and torque on this group
of atoms before the removal of forces? I am thinking of applying the
command fix rigid to this group of atoms, as that command can output
the total force and torque. But fix rigid command also does time
integration and this conflicts with the integration in the fix move
command. If there is any suggestion on how to get the total force and
torque, please let me know. Thank you.


I think for the total torque, I can calculate the peratom value by
defining my own variable. Then I can apply the compute/reduce command
to get a global value for the group of atoms. Hope this works.


2010/9/20 T GE <[email protected]>:

I don't think fix move does anything to the forces on its atoms,
rather it just ignores them. So if you dump them out
at the end of the timestep, aren't those the forces you want?

For torque, you'd have to compute that around the c-o-mass
yourself. Variables can do things like omega(group) - it
would be easy to add torque(group).

Also, you should not use fix rigid and fix move on the same
atoms - they will conflict.