Ideal strength and elastic instability in single-layer 8-Pmmn borophene

Abstract

Using first principle calculations based on density functional theory (DFT), we have investigated the mechanical properties of monolayer 8-Pmmn borophene, including ideal strength and critical strain. It was found that monolayer 8-Pmmn borophene can withstand stress up to 21.59 N m⁻¹ and 27.79 N m⁻¹ in a and b directions, respectively. The ultimate tensile strain along the a direction is about 0.155, and 0.16 along the b direction, which is larger than that of stripe borophene. Furthermore, the phonon dispersions under the three applied strains indicate that the mechanical failure in 8-Pmmn borophene is likely to originate from the elastic instability. Our study shows that 8-Pmmn borophene is a hard but flexible 2D material, and may potentially be useful in high-strain engineering applications.