Multi-phonon proton transfer pathway in a molecular organic ferroelectric crystal

Abstract

Computer simulations reveal how the ferroelectric transition in croconic acid crystals involves many degrees of freedom.

Centimeter-Sized Single Crystal of a One-Dimensional Lead-Free Mixed-Cation Perovskite Ferroelectric for Highly Polarization Sensitive Photodetection

“…In particular, some bulk single crystals of 2D hybrid perovskites have been synthesized recently, showing excellent anisotropic photonic performances. − This, combined with the ferroelectric properties, can further broaden the applications of anisotropic photonic semiconducting materials. Due to the built-in electric field caused by the spontaneous polarization inside the hybrid perovskite ferroelectric, the transport and separation of carriers can be promoted, thereby improving the performance of polarization-sensitive devices. − Moreover, the intrinsic bulk photovoltaic effect of hybrid perovskite ferroelectric crystals has found use in highly sensitive polarized light detection to reach high polarization ratios. , However, to date, most of the reported polarization-sensitive perovskite ferroelectric crystals are based on 2D lead-based halides, in which the lamellar growth preference of single crystals severely hinders the preparation of crystals and their application in devices based on a sandwich configuration (along the (110) orientation). − ,, Particularly, most of these crystals are lead-based materials, causing enormous issues for eco-friendly applications. In this context, it is urgent to explore a new way to effectively design environmentally friendly and easy-to-prepare anisotropic perovskite ferroelectric crystal candidates toward highly polarization sensitive photodetectors.…”

Organic ferroelectric croconic acid: a concise survey from bulk single crystals to thin films

“…In the second mechanism, the 8 H atoms get transferred in 4 steps; a pair in each step. Similarly, Okenyi et al 105 also predicted the minimum energy path to involve a pairwise consecutive transfer of H atoms. Both the groups utilized the ‘nudged elastic band’ algorithm 106 with vdW-DF2 107 exchange correlation functional to calculate the minimum energy path.…”

“…Nevertheless, there remains fundamental questions regarding the exact nature of polarization reversal, that are being pursued both theoretically and experimentally. 103,105 For example, how the motion of the 8 H atoms in a unit cell of CA during polarization reversal is, whether the proton transfer process is sequential, pairwise or collective, and what the minimum energy path for the reversal process is. To gain deeper insights into the mechanism of proton transfer, several groups have calculated the potential energy curve corresponding to the minimum energy path of the proton transfer event.…”

Ferroelectricity in organic materials: from materials characteristics tode novodesign

“…138 Furthermore, Walsh and coauthors described the ferroelectricity of the proton transfer ferroelectric croconic acid by selecting the correct subset of its phonon modes and provided a deeper look at proton transfer ferroelectrics. 26 Kinetic Monte Carlo simulations were used to study switching kinetics in organic ferroelectrics. Both hysteresis loops and depolarisation curves were simulated for a large range of temperatures and timescales to investigate different flipping modes in this material.…”

“…The displacive type phase transition occurring in the organic ferroelectrics is closely related to the dynamics of charges, ions and molecules. [26][27][28][29] The subtle change of an atomic or molecular position can give rise to symmetry breaking and thus a paraelectric-to-ferroelectric phase transition will take place. It needs to be noted that the order-disorder and displacive type phase transitions are not mutually exclusive.…”