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Calculation of Local Pressure Tensors in Systems with Many-Body Interactions

Hendrik Heinz1, Wolfgang Paul2, and Kurt Binder2. (1) Materials and Manufacturing Directorate, Air Force Research Laboratory, Bldg 654, suite 341, 2977 P Street, Wright-Patterson AFB, OH 45433, (2) Institute of Physics, University of Mainz, Staudinger Weg 7, Mainz, D-55099, Germany

Local pressures can be used to monitor inhomogeneous systems, interface tensions, or equilibration processes, and contribute to the overall pressure. The calculation of pressures in computer simulations has often been limited to systems with pairwise interactions between the particles or conditions of homogeneity. We suggest a method to calculate local pressures and pressure profiles in inhomogeneous systems with n-body interactions (n=2,3,4,.. ) [1]. The pressure across a local area consists of a kinetic contribution from the linear momentum of the particles, plus the resulting force due to all many-body interactions dissected by that area. To define dissection by a small area, the respective n-body interactions are divided into two geometric centers. Averages over larger subsystems with this method show consistency with the special cases of the method of Irving and Kirkwood [2], the method of planes [3], and the virial formula. The new method is illustrated with a numerical example.

[1] H. Heinz, W. Paul, K. Binder, Phys. Rev. E, 72, 066704 (2005). [2] J. H. Irving and J. G. Kirkwood, J. Chem. Phys. 18, 817 (1950). [3] B. D. Todd, D. J. Evans, and P. J. Daivis, Phys. Rev. E 52, 1627 (1995).

Web Page: PRE 72, 066704 (2005)