  The mechanical properties of single-layer black phosphrous under uniaxial
deformation are investigated using first-principles calculations. Both Young's
modulus and the ultimate strain are found to be highly anisotropic and
nonlinear as a result of its quasi-two-dimensional puckered structure.
Specifically, the in-plane Young's modulus is 44.0 GPa in the direction
perpendicular to the pucker, and 92.7 GPa in the parallel direction. The
ultimate strain is 0.48 and 0.20 in the perpendicular and parallel directions,
respectively.

Materials Science