Fig. 1: Molecular design for piezoelectric materials.
From: Large piezoelectric response in a Jahn-Teller distorted molecular metal halide
a The modification of a spherical cation into a quasi-spherical cation lowers molecular symmetry and enables dipole moment. b The selected Cl–Cu–Cl and Cl–Zn–Cl bond angles of the [CuCl4]2− and [ZnCl4]2− tetrahedrons, representing those that deviate from the ideal 109.5°. The Jahn-Teller active Cu2+ enhances the deformation of the inorganic geometry. c Comparison of the crystal structures of DABCO-CuCl4, EDABCO-CuCl4, and EDABCO-ZnCl4. The combination of quasi-spherical cation and Jahn-Teller distortion results in the piezoelectric active structure.
