Single Molecule Ferroelectrics via Conformational Inversion: An Electronic Structure Investigation

Ferroelectric materials can switch their polarization in response to an applied electric field. In this work, ferroelectricity at the single molecule level is proposed and investigated using density functional theory (DFT) calculations. Several bowl-shaped molecules, both synthetically reported and hypothetically proposed, are shown to invert polarization in response to external applied electric fields. Such a polarization inversion relies on the conformational change of a single molecule, unlike its traditional counterparts of which ferroelectricity originates from the switch of an asymmetrical polar unit cell in inorganic crystals, or from the polar polymer chain rotation of ferroelectric polymers. We discuss both structural and functional group factors in determining the inversion electric field and the design rules for good single molecule ferroelectrics. A conceptual multistate ferroelectric model is discussed for single molecule ferroelectrics.