Carbon nanotubes and graphene have paved the way for the next step in the evolution of
carbon materials. Among the novel forms of carbon allotropes is graphyne – a two-dimensional
lattice of sp–sp2-hybridized carbon atoms similar to graphene for which recent progress
has been made in synthesizing dehydrobenzoannulene precursors that form
subunits of graphyne. Here, we characterize the mechanical properties of single-atomiclayer
graphyne sheets by full atomistic first-principles-based ReaxFF molecular dynamics.
Atomistic modeling is carried out to determine its mechanical properties for both in-plane
and bending deformation including material failure, as well as intersheet adhesion. Unlike
graphene, the fracture strain and stress of graphyne depends strongly on the direction of
the applied strain and the alignment with carbon triple-bond linkages, ranging from 48.2
to 107.5 GPa with ultimate strains of 8.2–13.2%. The intersheet adhesion and out-of-plane
bending stiffnesses are comparable to graphene, despite the density of graphyne being only
one-half of that of graphene. Unlike graphene, the sparser carbon arrangement in graphyne
combined with the directional dependence on the acetylenic groups results in internal
stiffening dependent on the direction of applied loading, leading to a nonlinear stress–
strain behavior.