Prediction of ϕ-P and σ-P: Two New Strain-Interconvertible Phosphorene Allotropes

Abstract

In this study, we propose two new 2D phosphorene allotropes, ϕ-P and σ-P, and use density functional theory calculations to explore their structural, electronic, and mechanical properties. The atomic structure of ϕ-P is derived from phagraphene, a 2D carbon allotrope recently discovered using evolutionary algorithms. The ϕ-P phase is converted into σ-P by a pair of Stone-Wales-like transformations, and both are thermally and mechanically stable, similarly to other predicted phosphorene allotropes. Nudged elastic band calculations show that the two materials can be interconverted by application of uniaxial strain under specific conditions. These materials are semiconductors, with band gaps controlled by strain and stacking of layers, and the corresponding bulk phases are either metallic or have a small band gap. The charge carrier mobilities and mechanical properties under uniaxial tensile strain are highly anisotropic because of the structural features of these new phases. The ϕ-P and σ-P allotropes are valuable additions to the phosphorene family because of their ability of being interconverted by mechanical deformation, enabling dynamic control of morphology and physical properties of the material and of the preferential direction for charge transport, a feature that can be explored toward the design of novel applications in nanoscale electronics.