New phosphorene by phase combination with tunable electronic and mechanical properties

A series of new phosphorene allotropes, αβ-P, βγ-P, γδ-P, αγ-P, αδ-P, and βδ-P, produced via phase combination of four basic phosphorenes α-P, β-P, γ-P, and δ-P, are predicted using first-principles calculations. Their thermodynamic stabilities are confirmed by cohesive energy calculations. Their band alignments compared with the O₂/O₂⁻ redox potential suggest an improved chemical stability toward oxidative degradation in ambient conditions. These new mixed-phase phosphorene allotropes show attractive anisotropric electronic and mechanical properties. In particular, γδ-P shows the narrowest band gap (0.80 eV based on HSE06 calculations) and the highest negative Poisson ratio among all mixed and basic phosphorenes reported to date. The γδ-P allotrope additionally exhibits tunable electronic properties and a semiconductor-to-metal transition that can be induced via uniaxial strain.