Computer simulation of polyethylene crystals

Abstract

A suite of computer programs has been developed for the simulation of defects in polyethylene crystals. The programs assume model crystals in which intramolecular distortions are excluded and the molecular chains are straight and infinite in length. Intermolecular interactions are described by non-bonded interatomic potentials, and, for defect modelling, it is considered desirable to extend their ranges from the values used previously. In the present paper (Part 1), the simulation method is outlined and the potentials employed are described. The lattice parameters given by the potentials are presented and discussed, and the elastic contstants for these rigid-chain crystals are com-computed. The constants for the orthorhombic phase are significantly different from those calculated previously, and it is argued that this is due to the restriction of the range of atom-atom interactions in earlier studies. Elastic constants for the monoclinic phase are given here for the first time. The developments described provide for the simulation of defects in model polymer crystals reported in Parts 2 and 3.