Fig. 4: Directional superelasticity in GeSe ceramic crystal.
From: Reversible shuffle twinning yields anisotropic tensile superelasticity in ceramic GeSe
a, Loading direction dependence of superelasticity in GeSe. TEM images showing typical fabricated GeSe samples for PTP testing, featuring different bridge orientations with respect to the zigzag direction. Insets: SAED patterns of the tested samples. The zigzag direction of each sample is indexed by a red arrow, and the stripy domains generated owing to tensile strain are highlighted by blue dashed lines. The black dashed lines indicate the fracture of the tested samples under a large strain. Middle inset: schematic diagram illustrating the range of tensile directions for the appearance of superelasticity in GeSe. The balls represent the experimentally measured values of θ, among which the orange balls highlight the superelastic case and the blue balls highlight the elastic case. b, The calculated Young’s modulus of GeSe along different directions. Angle of 0° indicates the strain along the zigzag ([100]) direction. c, Poisson’s ratio and convergence coefficient τ along different directions. τ indicates the ease of convergence between a and b with axial tensile strain. Inset: the orientation of GeSe crystal. d, Top view of charge density difference between a GeSe structure with one Ge–Se pair rotated by 90° and one without bond rotation. Ge and Se atoms are coloured in purple and green, respectively. The red and blue bubbles indicate the increase and decrease of the charge density, corresponding to the electron dissipation and collection, respectively.
