Computational design of a ferroelectric framework material based on dipolar rotors.

In this work, we present a hierarchical approach to generate ferroelectric covalent frameworks based on rotatable polar groups. By using a multi-step workflow of increasing theoretical sophistication but also increasing computational costs, a unit cell with ferroelectric behavior can be generated for a given organic linker group. Starting with a basic point dipole model to find an appropriate unit cell, followed by a three-dimensional representation of the organic rotor, up to the full framework, each step confirms the desired attributes. This is achieved by using molecular dynamics and Monte Carlo Metropolis sampling in combination with the "Universal Force Field for Metall-Organic-Frameworks" (UFF4MOF) and the van der Waals corrected density functional tight-binding approach (known as GFN1-xTB) for the energy calculations. As a result, we demonstrate a covalent organic framework that is predicted to show a ferroelectric ground state that is stable up to temperatures beyond 100 K.