Syntax:
compute ID group-ID epair/atom
Examples:
compute 1 all epair/atom
Description:
Define a computation that computes the per-atom pairwise energy for each atom in a group.
The pairwise energy for each atom is computed by looping over its neighbors and computing the energy associated with the defined pair_style command for each I,J pair (divided by 2). Thus the sum of per-atom energy for all atoms should give the total pairwise energy of the system.
If two atoms interact and only one of them is in the compute group, the energy of the pairwise interaction is included in the per-atom energy of the atom in the group.
For force fields that include a contribution to the pairwise energy that is computed as part of dihedral terms (i.e. 1-4 interactions), this contribution is NOT included in the per-atom pairwise energy.
Computation of per-atom pairwise energy requires a loop thru the neighbor list and inter-processor communication, so it can be inefficient to compute/dump this quantity too frequently or to have multiple compute/dump commands, each of a epair/atom style.
Restrictions:
Some pair potentials do not allow the calculation of per-atom energy via this command. An error will be generated if this is the case.
Related commands: none
Default: none