**Title:** A new method for calculating the pressure profile by LAMMPS

**Presenter:** Takenobu Nakamura

**Affiliation:** Tohoku University WPI-AIMR

**Abstract:** Different from density or kinetic energy, the computation for local pressure
tensor has not been supported by LAMMPS. That is partly because the local pressure tensor
is not defined as a “per-atom” quantity but as a result of an interaction among several
atoms in a cluster potential. According to the literature **1**, the local pressure tensor
can be explicitly represented by using a contour integration. Using the representation,
we have developed a method to calculate the local pressure tensor along the radial axis
for a spherical material **2**. Additionally, we have recently developed a method for
calculating the 3-dimensional local pressure tensor with high accuracy **3**. Our method
exactly assigns the contribution of contour integration to each 3D bin without a numerical
approximation as in the previous method **4**. We have made a new command calculating local
pressure field for
(1) cuboids divided in a 3 dimensional grid pattern,
(2) planar bins sliced along 1 dimensional axis **5**,
(3) spherical bins sliced along the radial axis from a chosen center.
In this talk, after a brief introduction of the theoretical background of the method,
we will demonstrate a few application studies. We also show how to use the method in lammps.

**1** P. Schofield and J. R. Henderson, Proc. R. Soc. London, Ser. A 379, 231 (1982).

**2** T. Nakamura, W. Shinoda and T. Ikeshoji, J. Chem. Phys. 135, 094106 (2011).

**3** T. Nakamura, S. Kawamoto and W. Shionda in preparation (2013)

**4** O. H. S. Ollila, H. J. Risselada, M. Louhivuori, E. Lindahl, I. Vattulainen,
and S. J. Marrink, Phys. Rev. Lett. 102, 078101 (2009).

**5** E. Lindahl and O. Edholm, J. Chem. Phys. 113, 3882 (2000).