Theoretical exploration of mechanical and superconducting properties of two-dimensional Cairo penta-BP2: A first-principles study

Two-dimensional (2D) Cairo pentagon materials have attracted tremendous interest due to their exotic physical properties. Based on first-principles calculations, we predict that monolayer penta-BP2 is a promising Cairo pentagon-based 2D material simultaneously harboring a negative Poisson ratio and intrinsic superconductivity. The Poisson ratio exhibits strong anisotropy with alternating positive-negative signs, and its value along the diagonal direction is more negative than that of pentagraphene. The medium-strength coupling between the Fermi-surface electrons and a phonon mode majorly originating from the P(2 )dimers leads to a superconducting transition estimated to occur at T-c similar to 7.7 K. Moreover, we find that fluorination/chlorination can efficiently engineer the superconductivity and mechanical properties of penta-BP2: achieving higher T(c )of 9.6/10.5 K, turning Poisson's ratio from negative to positive and enhancing Young's modulus. These results render penta-BP2 an appealing platform to investigate unique superconductivity and mechanical properties in the Cairo pentagon lattice.

Automated summary

This study predicts a new 2D material, monolayer penta-BP2, which exhibits a negative Poisson ratio and intrinsic superconductivity based on the Cairo pentagon lattice. Fluorination/chlorination can efficiently engineer its superconductivity and mechanical properties, making it an appealing platform to investigate unique properties in the Cairo pentagon lattice.