Novel numerical method for calculating the pressure tensor in spherical coordinates for molecular systems

Takenobu Nakamura, Wataru Shinoda, and Tamio Ikeshoji

J. Chem. Phys. 135, 094106/1-10 (2011).

We propose a novel method for computing the pressure tensor along the radial axis of a molecular system with spherical symmetry. The proposed method uses the slice averaged pressure to improve the numerical stability and precision significantly. Simplified expressions of the local pressure are derived for a conventional molecular force field including non-bond, bond stretching, angle bending, and torsion interactions; these expressions are advantageous in terms of the computational cost. We also discuss an algorithm to avoid numerical singularity. Finally, the method is successfully applied to three different molecular systems, i.e., a water droplet in oil, a spherical micelle, and a liposome.