  Popgraphene (PopG) is a new 2D planar carbon allotrope which is composed of
$5-8-5$ carbon rings. PopG is intrinsically metallic and possesses excellent
thermal and mechanical stability. In this work, we report a detailed study of
the thermal effects on the mechanical properties of PopG membranes using
fully-atomistic reactive (ReaxFF) molecular dynamics simulations. Our results
showed that PopG presents very distinct fracture mechanisms depending on the
temperature and direction of the applied stretching. The main fracture dynamics
trends are temperature independent and exhibit an abrupt rupture followed by
fast crack propagation. The reason for this anisotropy is due to the fact that
y-direction stretching leads to a deformation in the shape of the rings that
cause the breaking of bonds in the pentagon-octagon and pentagon-pentagon ring
connections, which is not observed for the x-direction. PopG is less stiff than
graphene membranes, but the Young's modulus value is only 15% smaller.
