2014/03/31 by Jin-Wu Jiang, Harold S. Park · 1 citation
Physics and Astronomy · #cond-mat.mtrl-sci
paper · pdf · doi:10.1038/ncomms5727
published as Nature Communications 5, 4727 (2014) · Nature Communications, accepted
arxiv created 2014/08/02 · arxiv updated 2014/08/19
The Poisson's ratio is a fundamental mechanical property that relates the resulting lateral strain to applied axial strain. While this value can theoretically be negative, it is positive for nearly all materials, though negative values have been observed in so-called auxetic structures. However, nearly all auxetic materials are bulk materials whose microstructure has been specifically engineered to generate a negative Poisson's ratio. In the present work, we report using first principles calculations the existence of a negative Poisson's ratio in a single-layer, two-dimensional material, black phosphorus. In contrast to engineered bulk auxetics, this behavior is intrinsic for single layer black phosphorus, and originates from its unique, puckered structure, where the pucker can be regarded as a re-entrant structure that is comprised of two coupled orthogonal hinges. As a result of this atomic structure, a negative Poisson's ratio is observed in the out-of-plane direction under uniaxial deformation in the direction parallel to the pucker, with the Poisson's ratio becoming increasingly negative with both increased tension and compression. The puckered structure also results in highly anisotropic in-plane Poisson's ratios, which are found to be 0.4 in the direction perpendicular and 1.28 in the direction parallel to the pucker.