Mechanisms of Molecular Ferroelectrics Made Simple

TL;DR

This paper introduces a combined molecular dynamics and enhanced sampling methodology to simulate and understand the ferroelectric mechanisms in molecular ferroelectrics, validated on a specific compound with results aligning with experiments.

Contribution

It develops a novel simulation approach integrating polarized force fields and replica-exchange MD to elucidate ferroelectric switching and phase transitions in molecular ferroelectrics.

Findings

Simulated hysteresis loops match experimental data

Predicted Curie temperature around 600 K

Identified phase transition temperatures for enantiomers

Abstract

Molecular ferroelectrics have captured immense attention due to their superiority over inorganic oxide ferroelectrics, such as environmentally friendly, low-cost, flexible, foldable. However, the mechanisms of ferroelectric switching and phase transition for the molecular ferroelectrics are still missing, leaving the development of novel molecular ferroelectrics less efficient. In this work, we have provided a methodology combining molecular dynamics (MD) simulation on a polarized force field named polarized crystal charge (PCC) and enhanced sampling technique, replica-exchange molecular dynamics (REMD) to simulate such mechanisms. With this procedure, we have investigated a promising molecular ferroelectric material, (R)/(S)-3-quinuclidinol crystal. We have simulated the ferroelectric hysteresis loops of both enantiomers and obtained spontaneous polarization of 7/8 \mu C cm-2 and a corresponding coercive electric field of 15 kV cm-1. We also find the Curie temperature as 380/385 K for ferro-/para-electric phase transition of both enantiomers. All of the simulated results are highly compatible with experimental values. Besides of that, we predict a novel Curie temperature of about 600 K. This finding is further validated by principal component analysis (PCA). Our work would significantly promote the future exploration of multifunctional molecular ferroelectrics for the next generation of intelligent devices.