  Local pressures are important in the calculation of interface tensions and in
analyzing micromechanical behavior. The calculation of local pressures in
computer simulations has been limited to systems with pairwise interactions
between the particles, which is not sufficient for chemically detailed systems
with many-body potentials such as angles and torsions. We introduce a method to
calculate local pressures in systems with n-body interactions (n=2,3,4, . . .)
based on a micromechanical definition of the pressure tensor. The local
pressure consists of a kinetic contribution from the linear momentum of the
particles and an internal contribution from dissected many-body interactions by
infinitesimal areas. To define dissection by a small area, respective n-body
interactions are divided into two geometric centers, effectively reducing them
to two-body interactions. Consistency with hydrodynamics-derived formulas for
systems with two-body interactions (J. H. Irving and J. G. Kirkwood, J. Chem.
Phys. 18, 817 (1950)), for average cross-sectional pressures (B. D. Todd, D. J.
Evans, and P. J. Daivis, Phys. Rev. E 52, 1627 (1995)), and for volume averaged
pressures (virial formula) is shown. As a simple numerical example, we discuss
liquid propane in a cubic box. Local, crosssectional,and volume-averaged
pressures as well as relative contributions from two-body and three-body forces
are analyzed with the proposed method, showing full numerical equivalence with
the existing approaches. The method allows computing local pressures in the
presence of many-body interactions in atomistic simulations of complex
materials and biological systems.
