New Phosphorene by Phase Combination with Tunable Electronic and Mechanical Properties

A series of new phosphorene allotropes, alpha beta-P, beta gamma-P, gamma delta-P, alpha gamma-P, alpha delta-P, and beta delta-P, produced via phase combination of four basic phosphorenes alpha-P, beta-P, gamma-P, and delta-P, are predicted using first-principles calculations. Their thermodynamic stabilities are confirmed by cohesive energy calculations. Their band alignments compared with the O-2/O-2(-) 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, gamma delta-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 gamma delta-P allotrope additionally exhibits tunable electronic properties and a semiconductor-to-metal transition that can be induced via uniaxial strain.