Constant pressure molecular dynamics: Instantaneous external stress tensor in systems with periodic boundary conditions

Abstract

AbstractA stress tensor for systems with periodic boundary conditions is presented, which is different from the wellknown Irving‐Kirkwood expression. It is shown that it represents the external stress for particles initially in one of the cells of the periodic system. The statistical properties of the pressure, derived from the stress tensor, are discussed. It is demonstrated that this pressure can be used to simulate a constant pressure ‐ constant enthalpy ensemble. Constant pressure computer simulations on the basis of the proposed stress tensor are free of artificial parameters and the internal pressure is not constrained, in contrast to previously existing constant pressure simulation schemes.