Compute vdw and electrostatic force separately by group/group

Dear LAMMPS users,

I am trying to compute van der Waals and electrostatic forces separately by 'compute group/group' commands.
In my understanding, keyword 'pair' in group/group command only include van der Waals force and activating 'kspace yes' adds electrostatic force into the computed interaction energy.
Could you give your comments about the understanding and provide a way to achieve my purpose?
Thanks

Best regards,
Changjae Kim

Dear LAMMPS users,

I am trying to compute van der Waals and electrostatic forces separately by ‘compute group/group’ commands.
In my understanding, keyword ‘pair’ in group/group command only include van der Waals force and activating ‘kspace yes’ adds electrostatic force into the computed interaction energy.

no. kspace adds the long-range part to the short range electrostatic contribution tallied in the pair style.

please read up on ewald summation and how it works.

Could you give your comments about the understanding and provide a way to achieve my purpose?

it is not possible to do this in a normal run. the function to compute pairwise energy and force used by compute group/group does not separate the different contributions to the force and energy.

the only way to get those separately is to do a normal run, record a trajectory and then do two rerun commands where one only have the force field contribution from from the non-coulomb part and the other from the coulomb part.

axel.