We demonstrate graphitic packings of collapsed single-, double-, and triple-walled carbon nanotubes (CNTs) into bundles, which are of interest for the development of high-performance lightweight materials. Analysis of the van der Waals interaction of collapsed nanotubes with large widths (>5 nm) and direct atomistic calculations based on density functional-based tight-binding extended with pair-wise Lennard-Jones interactions, reveal the energetic advantage of a stacking with dislocation mode over regular and dislocation-dipole stackings, as well as over the side-by-side orientation of collapsed tubes. This unusual mode - seen previously in the transmission electron microscopy of collapsed CNT bundles - involves a relative nm-scale stacking shift combined with an asymmetric bulging of the CNT edges to permit the formation of large van der Waals graphitic interfaces between collapsed CNTs. As part of this paper, we present the first mesoscale model for collapsed CNT bundles described with mesoscopic forces derived from the atomic scale. The model features accuracy and computational efficiency, which are attributes required for the further development of multiscale models of fiber materials based on collapsed CNTs.
Bibliographical noteFunding Information:
This work was supported by NASA's Space Technology Research Grant NNX16AE03G and by the Institute for Ultra-Strong Composites by Computational Design , Grant NNX17AJ32G . Resources supporting this work were provided by the Minnesota Supercomputing Institute and by NASA High End Computing Program through the NASA Advanced Supercomputing Division at Ames Research Center. TD thanks Hanse Wissenschaftskolleg Institute for Advanced Study Delmenhorst, Germany, for hospitality.
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