Formation of helices in graphene nanoribbons under torsion

Nikiforov, Ilia and Hourahine, Benjamin and Frauenheim, Thomas and Dumitrică, Traian (2014) Formation of helices in graphene nanoribbons under torsion. Journal of Physical Chemistry Letters, 5 (23). 4083–4087. ISSN 1948-7185 (

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We use objective boundary conditions and self-consistent charge density-functional-based tight-binding to simulate at the atomistic scale the formation of helices in narrow graphene nanoribbons with armchair edges terminated with fluorine and hydrogen. We interpret the microscopic data using an inextensible, unshearable elastic rod model, which considers both bending and torsional strains. When fitted to the atomistic data, the simple rod model uses closed-form solutions for a cubic equation to predict the strain energy and morphology at a given twist angle and the crossover point between pure torsion and a helix. Our modeling and simulation bring key insights into the origin of the helical graphene morphologies stored inside of carbon nanotubes. They can be useful for designing chiral nanoribbons with tailored properties.