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Abstract
The molecular dynamics package DL_POLY has at its heart a number of versatile and efficient dynamics algorithms that can readily be adapted to extend the application of this code well beyond the time and length scales typically associated with atomistic simulations. In order to achieve this, it is necessary to substitute the appropriate interparticle potentials and forces in place of the default functional forms in DL_POLY, which are mainly suitable for molecular systems. To facilitate this, it may be required to incorporate additional factors, into the simulation, such as velocity-dependent dissipation effects (friction), rotational degrees of freedom and non-spherosymmetric forces. In this paper, we will discuss some of the practical details of implementing these changes to DL_POLY (version 2) together with applications of discrete particle dynamics methods, such as dissipative particle dynamics (DPD) and granular dynamics (GD) (also known as the discrete or distinct element method, DEM) to particle packing in composite systems and pharmaceutical powders. We also consider how well the approach of simulating particles of arbitrary shape using rigid assemblies of fused soft spheres (each individually interacting via pairwise continuous potentials) compares to true hard-body simulations of polygonal particles.
Acknowledgements
The authors are grateful to a number of funding bodies for financial support for the various parts of this work, including the Engineering and Physical Sciences Research Council (EPSRC), Pfizer Inc., the US Air Force (under contract S-709-009-014/D) and the US Army European Research Office (under contract N6255-020C9014). The use of data from the PhD thesis of Sameer S. Rahatekar (figure ) is acknowledged.