Super-stretchable borophene

Abstract

Recent success in the synthesis of the two-dimensional borophene on silver substrates has attracted strong interest in exploring its extraordinary properties for potential technological applications. The single-layer borophene has a buckled structure with atomic ridges. By using the first-principles density functional theory calculations, we show that the two-dimensional borophene is highly stretchable with strong anisotropy The strain-to-failure in the direction along the atomic ridges is nearly twice as large as that across the atomic ridges. The straining-induced flattening and the subsequent stretch of the flat borophene are accounted for the large strain-to-failure for tension along the atomic ridges. We also investigated the mechanics of monolayer borophene under biaxial tension and we found that the biaxial tension increases the strength across the atomic ridges but decreases the failure strain along the atomic ridges. Furthermore, when the bilayer borophene is stretched along the cross-plane direction, the strength and failure strain of the bilalyer borophene are much higher than those of the bilayer graphene due to the very strong inter-layer chemical bonding.

Molecular dynamics simulations for mechanical properties of borophene: parameterization of valence force field model and Stillinger-Weber potential

“…Good agreements are achieved for the three acoustic branches in the long wavelength limit. Similar phonon dispersion can be found from other ab initio calculations262938. There is no imaginary mode from the VFF model, which appears in the ab initio calculations for the flexure mode in the long wave limit26282938.…”

“…Free edges in the borophene nanoribbon were found to be important for mechanical, electronic, magnetic, and thermal transport properties343536. The strain effect has been studied for mechanical properties283738, or magnetic properties in borophene39. Several defects were predicted to cause considerable effects on the anisotropic mechanical properties of the borophene30.…”

The electronic, optical, and thermodynamic properties of borophene from first-principles calculations

“…However, the ZA branch has imaginary frequency along Γ-X direction. Negative frequency means that the restoring forces cannot be generated for the ZA branch 51 .…”

“…In fact, recent studies have suggested that the tensile strength of borophene is dictated by out-of-plane soft-mode phonon instability under biaxial tension or uniaxial tension along the a direction 52 , and free-standing borophene is instable even under high tensile stress 51 .…”

Stability and strength of atomically thin borophene from first principles calculations

“…The following first principles calculations have predicted that striped borophene possesses remarkable mechanical properties 35,36 , which may rival graphene 16 . However, phonon instability in striped borophene is observed 37 , which may challenge previous results demonstrating that borophene is stiffer than graphene along a direction 16,35,36 . striped borophene are evaluated using first principles calculations.…”