Bending poisson effect in two-dimensional crystals

As the Poisson effect formulates, lateral strains in a material can be caused by a uniaxial stress in the perpendicular direction, but no net lateral strain should be induced in a thin homogeneous elastic plate subjected to a pure bending load. Here, we demonstrated by ab initio simulations that significant exotic lateral strains can be induced by pure bending in two-dimensional crystals, in which the lateral components of chemical bonds can respond to bending curvature directly. The bending Poisson ratio, defined as the ratio of lateral strain to the curvature, is a function of curvature depending on chemical constitution, bonding structure, and atomic interaction of the crystal, and is anisotropic.