Bending-induced extension in two-dimensional crystals

TL;DR

This paper reveals that two-dimensional crystals can experience significant overall tensile strain due to bending, caused by asymmetric bond responses, challenging classical elasticity theory.

Contribution

It introduces the discovery of bending-induced extension in 2D crystals, supported by ab initio simulations, highlighting a new mechanical behavior not predicted by classical models.

Findings

Bending induces significant tensile strain in 2D crystals.

The tensile strain is a power function of curvature.

The effect is caused by asymmetric bond and electron density responses.

Abstract

According to the classical theory of elasticity, a plate subjected to a bending moment always deflects with symmetric tensile and compressive strains in its two sides, without overall deformation perpendicular to the bending moment. Here, we find by ab initio simulations that significant overall tensile strain can be induced by pure bending in a wide range of two-dimensional crystals perpendicular to the bending moment, just like an accordion being bent to open. This accordion effect is raised by asymmetric response of chemical bonds and electron density to the bending curvature, with the tensile strain being a power function of the curvature.