Formation of Helices in Graphene Nanoribbons under Torsion.
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.
†Department of Mechanical Engineering, University of Minnesota, 111 Church Street Southeast, Minneapolis, Minnesota 55455, United States.
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Nikiforov
‡Department of Physics, SUPA, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG, United Kingdom.
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Hourahine
¶BCCMS, Universität Bremen, Am Fallturm 1, D-28359 Bremen, Germany.
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Frauenheim
†Department of Mechanical Engineering, University of Minnesota, 111 Church Street Southeast, Minneapolis, Minnesota 55455, United States.
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Dumitrică
SCC-DFTB; carbon; graphene nanoribbons; nanomechanics; objective molecular dynamics; rods