A LOOSE-COUPLING, CONSTANT-PRESSURE, MOLECULAR-DYNAMICS ALGORITHM FOR USE IN THE MODELING OF POLYMER MATERIALS

This paper describes in detail a "constant-pressure" molecular dynamics algorithm which has been developed to facilitate the modelling of bulk amorphous polymeric systems. The algorithm is based on the "loose coupling" method of Berendsen et al. [J. Chem. Phys. 81 (1984) 3684] in which the difference between the externally applied tensorial pressure field and the internally measured pressure are relaxed out by coupling this imbalance to changes in the shape and size of the primary cell. Unlike the alternative Rahman-Parrinello technique it does not generate a well-defined ensemble. It does, however, have practical advantages which make it preferable, particularly when measuring non-equilibrium properties of elasto-plastic materials.