Practical atomistic models of carbon fiber surfaces with tuneable topology and topography

Abstract The atomic-scale surface structure of carbon fiber is not well resolved. This information would advance knowledge of structure-property relationships for carbon fiber in complex interfacial environments, e.g. composites. Molecular simulations could provide these insights, via incorporation of topological and topographical complexity into surface models of carbon fiber to explore this effect. This requires use of highly-specialized potentials. However, out of practicality, the majority of fiber interfacial simulations use multi-element, fixed-topology force-fields that are not harmonized with leading carbon-only potentials, resulting in the widespread adoption of graphite as a surrogate model of carbon fiber in interfacial simulations, neglecting complexity. To address this, a process for generating complex yet practical structural models of the carbon fiber surface is introduced. A carbon-only potential is used to generate topologically and topographically rich surfaces via annealing molecular dynamics simulations and manipulation of periodic boundary conditions. This produces fiber surfaces featuring edges, holes, convergent sheet boundaries, topological defects, amongst other structures. Key parameters of the process influence this complexity, ensuring structural tuneability of the resultant substrate. These structures are transposed into a multi-element molecular mechanics format. This approach provides practical structural models for immediate application in any interfacial simulation between carbon fiber and its complex environment.