Negative In-Plane Poisson's Ratio for Single Layer Black Phosphorus: An Atomistic Simulation Study

We utilized molecular statics (MS) simulations to investigate the auxeticity of single layer black phosphorus (SLBP). Our simulation results show that the SLBP has a negative in-plane Poisson's ratio in the zigzag direction when the applied strain along the armchair direction exceeds 0.018. We show that the interplay between bond stretching and bond rotating modes determines the in-plane Poisson's ratio behavior. While the bond stretching mode always tends to increase the in-plane auxeticity, the bond rotating mode might increase or decrease the in-plane auxeticity. Furthermore, we show that graphite also exhibits an in-plane negative Poisson's ratio at finite strains due to a similar mechanism