The small systems that are important for nanotechnology may not be "small" when viewed from the standpoint of simulations performed using models expressed at fully atomistic detail. This problem can be especially severe when the system contains amorphous polymers, because of the large range of distance and time scales that describe the relaxation of these systems. The efficiency of the simulation can be improved by resorting to a coarse-grained model for the chains, but often at the expense of an unambiguous identification of the model with any particular real polymer. This difficulty has prompted recent interest in the design, performance, and analysis of simulations that bridge representations of a single system that differ in structural detail.1 In the present context, we require a method where there is a two-way (reversible) path connecting a coarse-grained and fully atomistic description of the same system

This chapter will review the generation of free-standing thin films and fibers with a coarse-grained simulation method on a high coordination lattice,23 performed in a manner that allows accurate reverse-mapping of individual replicas to a fully atomistic representation in continuous space.4 After describing some of the properties of these films and fibers, we will present some new information about the limits on the stability of the models of these nanofibers.

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