Dear LAMMPS users,
I am trying to calculate the system pressure based on the virial theorem as compute_presssure does.
By comparing the virial part (force f dot location x), my calculation deviate much from the result in compute_pressure.cpp, which is from the function of virial_fdotr_compute() in pair.cpp.
I used the same mathod in virial_fdotr_compute(), which sums f[i][0-2] dot x[i][0-2] for owned and ghost atoms.
I checked the differences by decoupling force and location, and found the location x[i][0-2] are the same, but the forces are not.
I read through the developer guide from LAMMPS, and found that after the force calculation by pair->compute(), there is comm->reverse_comm(), which maps forces on ghost atoms back to owned atoms.
Because the virial from LAMMPS is calculated during pair->compute(), before comm->reverse_comm(), and I am trying to calculate virial during fix->post_force(), after comm->reverse_comm().
I suppose the comm->reverse_comm() process makes the differences in calculating virial. But I don’t know how it works and how I should solve that if this process results in the differences.
Thanks in advance for any advice and comments regarding this issue.