Mechanical Twinning in Phosphorene

TL;DR

This study explores how phosphorene deforms under tensile strain, revealing unique twin-like deformation mechanisms that influence its failure behavior, with implications for nano-electronic-mechanical applications.

Contribution

It uncovers the homogeneous and heterogeneous twin-like deformation mechanisms in phosphorene sheets and nanoribbons, highlighting the effects of vacancies and the failure process.

Findings

Homogeneous twin-like deformation increases failure strain.

Vacancies promote heterogeneous twin nucleation at lower strains.

Twin propagation is interrupted by edge fracture.

Abstract

We investigate the deformation and failure mechanisms of phosphorene sheet and nanoribbons under uniaxial tensile strain along the zigzag direction using the density functional tight-binding method. Surprisingly, twin-like deformation occurs homogenously across the phosphorene sheet, which significantly increases its failure strain. Vacancies within the sheet lead to the heterogeneous nucleation of twins at a lower critical strain which, subsequently, propagate across the entire sheet. Twin-like deformation always occurs heterogeneously in phosphorene nanoribbons (with or without vacancies). Propagation of the twins is interrupted by fracture which initiates along the ribbon edge. The underlying mechanism is bond breaking between the atoms within phosphorene puckers and simultaneous bond formation between the atoms in neighboring puckers. This unusual deformation behavior in phosphorene may be exploited in novel nano-electronic-mechanical applications.