title: Defect-detriment to graphene strength is concealed by local probe: the topological and geometrical effects.
abstract: Defects in solids commonly limit mechanical performance of materials by reducing their rigidity and strength. However, topological defects also induce a prominent geometrical effect in addition to local stress buildup, which is especially pronounced in two-dimensional crystals. These dual roles of defects modulate mechanical responses of the material under local and global probes in very different ways. We demonstrate through atomistic simulations and theoretical analysis that local response of two-dimensional crystals can even be stiffened and strengthened by topological defects as the structure under indentation features a positive Gaussian curvature, while softened and weakened mechanical responses are measured at locations with negative Gaussian curvatures. These findings shed lights on mechanical characterization of two-dimensional materials in general. The geometrical effect of topological defects also adds a new dimension to material design, in the scenario of geometrical and topological engineering.
authors.affiliation: Applied Mechanics Laboratory, Department of Engineering Mechanics and Center for Nano and Micro Mechanics, Tsinghua University , Beijing 100084, China.
authors.forename: Zhigong
authors.initials: Z
authors.lastname: Song
authors.forename: Vasilii I
authors.initials: VI
authors.lastname: Artyukhov
authors.forename: Jian
authors.initials: J
authors.lastname: Wu
authors.forename: Boris I
authors.initials: BI
authors.lastname: Yakobson
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Xu
keywords: geometrical effect; graphene; material strength; mechanical properties; nanoindentation; topological effect