Pressure in rigid body molecular dynamics

Abstract We present a detailed derivation of the expression for the pressure in MD simulations that contain rigid bodies, where two equivalent formulations have been developed. One of these formulations was used in HOOMD-blue v1.x, but implemented incorrectly. We point out the precise reason for this implementation issue, the difference with the current and correct implementation in HOOMD-blue v2.x, and lessons learned. We perform numerical validation tests using dumbbell models, a mixture of cubic and spherical particles, and the SPC/E water model.