[lammps-users] Set different force to all the atoms

I have a question about adding force to all the atoms in a cubic.

Specific force has to be applied to all the the atoms. And the force is different on different atoms and there is no relation between different forces.

By using ‘addforce’ or ‘setforce’ command, a force can only applied to a group of atoms. However, there is a limit of 32 of the max number of groups, so it is impossible to set each atom to a dependent group.

I want to know what I can do to solve the problem. Thanks.

Is this a one-time initiation step? If it is, can you calculate what the velocity for each atom ought to be due to its particular force and then just specify a velocity for each atom in the data file?


If you're using NEB or some other method to compute a specific
force on each of many atoms every timestep, then either:

a) you're doing this external to LAMMPS, in which case you
will want to write a fix that reads the file of forces and applies
them to the appropriate atoms, or

b) you're doing this inside LAMMPS with a fix you wrote yourself,
in which case you should just apply the forces directly to the atoms

If you want to do something else, please describe it in more detail.