High anisotropy of fully hydrogenated borophene

TL;DR

This study investigates the highly anisotropic mechanical properties and phonon stability of fully hydrogenated borophene (borophane) under various strains using first principles calculations, revealing its potential for strain engineering.

Contribution

It provides the first detailed analysis of borophane's anisotropic mechanical behavior and phonon stability under strain, highlighting its unique properties compared to other 2D materials.

Findings

Borophane exhibits highly anisotropic ultimate tensile strains (0.12 along a, 0.30 along b)

Phonon stability persists up to 5-15% uniaxial and 9% biaxial strains

Mechanical failure likely originates from phonon instability

Abstract

We have studied the mechanical properties and phonon dispersions of fully hydrogenated borophene (borophane) under strains by first principles calculations. Uniaxial tensile strains along the a- and b-direction, respectively, and biaxial tensile strain have been considered. Our results show that the mechanical properties and phonon stability of borophane are both highly anisotropic. The ultimate tensile strain along the a-direction is only 0.12, but it can be as large as 0.30 along the b-direction. Compared to borophene and other 2D materials (graphene, graphane, silicene, silicane, h-BN, phosphorene and MoS2), borophane presents the most remarkable anisotropy in in-plane ultimate strain, which is very important for strain engineering. Furthermore, the phonon dispersions under the three applied strains indicate that borophane can withstand up to 5% and 15% uniaxial tensile strain along the a- and b-direction, respectively, and 9% biaxial tensile strain, indicating that mechanical failure in borophane is likely to originate from phonon instability.