Temperature-Diversified Anisotropic Superelasticity and Ferroelasticity in a 3‑Methyl-4-Nitrobenzoic Acid Crystal

In diffusion-less plastic deformation, crystalline materials deform without losing crystallinity by keeping the relative positions of atoms and/or molecules. The deformation in a direction-independent manner is achieved in polycrystalline inorganic materials comprised of isotropic spherical atoms. On the other hand, single crystals especially constructed by anisotropic molecules are expected to show anisotropic responses in the deformation. Herein we demonstrate anisotropic mechanical behaviors in a single crystal of 3-methyl-4-nitrobenzoic acid: shear direction-dependent selectivity between superelasticity and ferroelasticity. Superelasticity in two opposite directions based on two-way, mechanically induced phase transition is also noteworthy. These behaviors are unprecedented in so-called shape-memory alloys and characterize the multiplicity of organosuperelasticity and organoferroelasticity from the viewpoint of anisotropy in mechanical deformation.