Negative Thermal Expansion and Electric/Magnetic Properties of Supramolecular Ionic Crystals

The mechanism of negative thermal expansion （NTE） in molecular crystals is not well understood due to the wide variety of factors involved. On the other hand, the involvement of diverse factors suggests that NTE can be hybridized with other physical properties. Molecular motion in crystals can be a factor of NTE through increasing entropy, which is difficult to realize. As an effective way to achieve molecular motion in crystals, we propose a supramolecular approach. In this paper, we introduce uniaxial and multiaxial NTE based on the supramolecular approach, relaxor ferroelectricity associated with molecular motion and unique magnetic properties due to molecular rearrangements associated with NTE.