  In this investigation, we conducted density functional theory simulations to
explore the mechanical responses of single-layer GeP, GeAs, SiP and SiAs. In
particular, we explored the possibility of band-gap engineering in these 2D
structures through different mechanical loading conditions.First-principles
results of uniaxial tensile simulations confirm anisotropic mechanical
responses of these novel 2D structures, with considerably higher elastic
modulus, tensile strength and stretchability along the zigzag direction as
compared with the armchair direction. Notably, the stretchability of considered
monolayers along the zigzag direction was found to be slightly higher than that
of the single-layer graphene and h-BN. The electronic band-gaps of energy
minimized single-layer SiP, SiAs, GeP and GeAs were estimated by HSE06 method
to be 2.58 eV, 2.3 eV, 2.24 eV and 1.98 eV, respectively. Our results highlight
the strain tuneable band-gap character in single-layer SiP, SiAs, GeP and GeAs
and suggest that various mechanical loading conditions can be employed to
finely narrow the electronic band-gaps in these structures.
