[lammps-users] FW: Ensemble Stress by LAMMPS

Lammps only provides the stress per-atom (dump). How can I use them to
formulate the stress of whole ensemble? A simple averaging operation
(based on the assumption that the atom's volume does not change)
seemingly does not provide correct answers. Thanks for your attention!

Hugh -

If you do a simulation of a periodic box of a given total volume and
dump per-atom stress = sxx syy szz to a file for each snapshot ... then
if you sum the sxx, syy, szz values to a single quantity (3N
values) ... you should get

pressure of system = - sum / volume / 3

where pressure is the thermo print-out. This is in accord with the
formula for per-atoms stress on this page of the LAMMPS doc: