Poisson's ratio of two-dimensional hexagonal materials under finite strains

Herein, we developed a bead-spring model to predict the Poisson's ratios of two-dimensional hexagonal materials under finite strains. The predicted strain-dependent Poisson's ratios were supported by simulations. The bounds on the Poisson's ratios of two-dimensional hexagonal materials under finite strains (-1/3, +infinity) were established. The underlying mechanism for the strain-dependent Poisson's ratios was uncovered as the interplay between bond stretching and angle bending during the stretching. These findings indicate that, even for the simplified material system under finite strains, there is no upper bound on the Poisson's ratios, and that there is plenty of room for strain-engineering the Poisson's ratios.