# Calculate the moment on a surface

Hi there,
Now I am running a bending test by applying a bending deformation on the sample ends. I am wondering how to calculate the bending moment response on the sample ends.
Best,
Haidong

How about dump the atoms at both ends. Compare their coordinates

in the bending direction. Calculate the difference.

Steve

Hi Steve,
What you said is a good method to calculate the bending angle (displacement), while I would like to calculate the bending moment (force) as a response to the applied bending angle.

On an arbitrary plane with arbitrary forces, as a general example, all the forces can be expressed by equivalent a force and a moment. The force is associated with the normal and shear stresses, which are pressure on the surface in LAMMPS. However, I am still wondering how to calculate the moment from the atom forces.
Best,
Haidong

You can also dump the forces on any atoms. Or you can sum the

forces in LAMMPS on any group of atoms. Or multiple groups

of atoms.

Steve