  Based on first-principles calculations, we study systematically the ideal
tensile stress-strain relations of three monoatomic group-V monolayer two
dimensional (2D) materials with buckled honeycomb lattices: blue phosphorene,
arsenene, and antimonene. The ideal strengths and critical strains for these 2D
materials are investigated under uniaxial and equibiaxial strains. It is found
that the ideal strengths decrease significantly as the atomic number increases,
while the critical strains change not so much. In particular, the ideal
strength of antimonene along armchair direction is found to exceed Griffith
strength limit. The distributions of charge density, buckling heights, bond
lengths, and bond angles are also studied under different types of strains. It
can be concluded that the critical strain is determined by the stretch and
rotation of bonds simultaneously. Furthermore, the phonon dispersions, phonon
instabilities, and failure mechanism of these materials under three types of
strains are also calculated and explored.
