It is widely anticipated that many future materials will be engineered at the nano-scale, be comprised of dissimilar materials, and possess multi-functional properties and behaviour. In coming decades, in silico prediction and testing will be commonplace for these materials, in both academia and industry, given the increasing capabilities and diminishing costs of high performance computing. There is intense current interest in use of 2-dimensional (2-d) nano-materials for these applications, including graphene and clay minerals. This presents a major challenge for simulation technology, as one has to describe a vast number of atomic interactions in the vicinity of the surface of the 2-d nanoparticle, while simultaneously accounting for how these interactions affect the properties on much larger length-scales. We present here several studies on 2-d nanomaterials that use a variety of connected single-scale simulations. Through matching quantum-mechanically derived energy profiles of graphene flakes moving over each other, we have created a classical molecular dynamics forcefield to capture the friction of sliding graphene flakes. This forcefield is able to describe the superlubric behaviour of graphene flakes on graphite observed experimentally and, from our simulations, we can determine the underlying atomistic mechanisms. Using coarse-grained molecular dynamics derived from atomistic molecular dynamics, we show the intercalation of polymer molecules into clay tactoids to form nanocomposites and their tendency to disperse or aggregate, depending on the chemical identity of the polymer and clay surface. Finally, we have implemented a multiscale model based on the heterogeneous multiscale method, where a finite element model of constitutive equations is directly replaced by molecular dynamics simulations. Such an approach allows us to simulate molecular systems with realistic boundary conditions which capture the dynamic and localization effects arising at the continuum level. We have used this model to study the toughness of epoxy-graphene composites. Our simulations provide insights into the mechanisms that lead to the emergence of brittle continuum behaviour from an atomistic ductile material.

From quantum to continuum: Multi-scale modelling of nanocomposites

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.