A Piezoelectric Molecular Cocrystal with Unconventional $\pi$-Stacking
Abstract
We demonstrate the crystallization of a polar octafluoronaphthalene (OFN, \OFN)--phthalazine (Phth, \Phth) cocrystal, formed in a 1:2 ratio by slow evaporation. The crystal structure and vibrational properties of the cocrystal were determined using powder/single-crystal X-ray diffraction (XRD) and Fourier-Transform Infrared (FTIR) spectroscopy, and confirmed with density functional theory (DFT) and density functional perturbation theory (DFPT) calculations. The molecular -stacking of aromatic rings is unconventional compared with other arene--perfluoroarene cocrystals. Phth molecules are offset and misaligned with respect to the major axis of OFN due to electrostatic repulsion between N and F atoms, enabling overall electric polarization attributed to the dipole moment of Phth. Our calculations show that OFN:2Phth is an insulator with a band gap of 2.4 eV. The electric polarization was calculated to be 7.1 \muC, while the shear piezoelectric coefficient () may be as large as 11.4 pC N.
Cite
@article{arxiv.2505.06095,
title = {A Piezoelectric Molecular Cocrystal with Unconventional $\pi$-Stacking},
author = {Samuel G. Dunning and Aldo Raeliarijaona and Piotr A. Guńka and Anirudh Hari and Dongzhou Zhang and Ronald E. Cohen and Timothy A. Strobel},
journal= {arXiv preprint arXiv:2505.06095},
year = {2025}
}