title: Multiwalled nanotube faceting unravelled.
abstract: Nanotubes show great promise for miniaturizing advanced technologies. Their exceptional physical properties are intimately related to their morphological and crystal structure. Circumferential faceting of multiwalled nanotubes reinforces their mechanical strength and alters their tribological and electronic properties. Here, the nature of this important phenomenon is fully rationalized in terms of interlayer registry patterns. Regardless of the nanotube identity (that is, diameter, chirality, chemical composition), faceting requires the matching of the chiral angles of adjacent layers. Above a critical diameter that corresponds well with experimental results, achiral multiwalled nanotubes display evenly spaced extended axial facets whose number equals the interlayer difference in circumferential unit cells. Elongated helical facets, commonly observed in experiment, appear in nanotubes that exhibit small interlayer chiral angle mismatch. When the wall chiralities are uncorrelated, faceting is suppressed and outer layer corrugation, which is induced by the Moiré superlattice, is obtained in agreement with experiments. Finally, we offer an explanation for the higher incidence of faceting in multiwalled boron nitride nanotubes with respect to their carbon-based counterparts.
authors.affiliation: Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Raymond and Beverly Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Itai
authors.initials: I
authors.lastname: Leven
authors.affiliation: International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.|CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Guerra
authors.affiliation: International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.|CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Vanossi
authors.affiliation: International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.|CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy.|The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy.
authors.forename: Erio
authors.initials: E
authors.lastname: Tosatti
authors.affiliation: Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Raymond and Beverly Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Oded
authors.initials: O
authors.lastname: Hod