Flexoelectricity of largely deformed graphene crumple nano sheet subject to hydrostatic pressure

We perform molecular dynamics simulations combined with a charge-dipole model to investigate the flexoelectricity evolved from the largely deformed stable graphene crumples. Spherically compressed deformation was adopted to circular, square, and equilateral triangular graphene sheets and analyzed their stability. Our analysis indicates that self-adhesion leads to irreversible graphene crumpling, which is determined by the interplay between bending energy and adhesion energy. Higher-order deformations of the crumpled structure generate flexoelectric effects, resulting in a non-zero dipole moment governed by asymmetric carbon–carbon bond bending and bond stretching. When the stabilized graphene crumples subjected to tensile stretching, we observed that the dipole moment of crumpled graphene increases linearly with strain, which highlights the piezoelectric characteristics induced by the flexoelectric effect. Among the different shapes, equilateral triangular graphene exhibits the largest dipole moment variation compared to square and circular graphene sheets. The steep dipole moment response suggests that crumpled graphene structures are promising candidates for piezoelectric applications.