Molecular Dynamics Simulation of Carbon Nanotube Based Gears

This is an early draft of a paper to appear in the journal Nanotechnology. The published version is here.


Jie Han, MRJ, Inc. at NASA Ames Research Center, Al Globus, MRJ, Inc. at NASA Ames Research Center, Richard Jaffe, NASA Ames Research Center, and Glenn Deardorff, Sterling Software at NASA Ames Research Center.


We used molecular dynamics to investigate the properties and design space of molecular gears fashioned from carbon nanotubes with teeth added via a benzyne reaction known to occur with C60 [Hoke 92]. A modified, parallelized version of Brenner's potential [Brenner 90] was used to model interatomic forces within each molecule. A Leonard-Jones 6-12 potential [Allen 87] was used for forces between molecules. One gear was powered by forcing the atoms near the end of the buckytube to rotate, and a second gear was allowed to rotate by keeping the atoms near the end of its buckytube on a cylinder. The meshing aromatic gear teeth transfer angular momentum from the powered gear to the driven gear. A number of gear and gear/shaft configurations were simulated. Cases in vacuum and with an inert atmosphere were examined. In an extension to molecular dynamics technology, some simulations used a thermostat on the atmosphere while the hydrocarbon gear's temperature was allowed to fluctuate. This models cooling the gears with an atmosphere. Results suggest that these gears can operate at up to 50-100 gigahertz in a vacuum or inert atmosphere at room temperature. The failure mode involves tooth slip, not bond breaking, so failed gears can be returned to operation by lowering temperature and/or rotation rate. Videos and atomic trajectory files in xyz format are presented.

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NAS Web Work: Al Globus