  The graphene-like two-dimensional (2D) silicon carbide or siligraphene has
attracted remarkable attentions, owing to its fascinating physical properties.
Nevertheless, the first high-quality siligraphene, i.e., monolayer Si9C15 was
synthesised very recently, which exhibits an excellent semiconducting
behaviour. In this work, we investigate the mechanical properties of Si9C15
siligraphene by using atomistic simulations including density functional theory
(DFT) calculations and molecular dynamics (MD) simulations. Both methods
confirm the existence of intrinsic negative Poisson's ratios in Si9C15
siligraphene, which, as illustrated by MD simulations, is attributed to the
tension-induced de-wrinkling behaviours of its intrinsic rippled configuration.
Different de-wrinkling behaviours are observed in different directions of
Si9C15 siligraphene, which result in the anisotropy of its auxetic property.
The fracture property of Si9C15 siligraphene is similarly anisotropic, but
relatively large fracture strains are observed in different orientations,
indicating the stretchability of Si9C15 siligraphene. The stretchability
together with the strain-sensitive bandgap of Si9C15 siligraphene observed in
DFT calculations indicates the effectiveness of strain engineering in
modulating its electronic property. The combination of unique auxetic property,
excellent mechanical property and tunable electronic property may render Si9C15
siligraphene a novel 2D material with multifunctional applications.
