Tiny Structural Features and their Giant Consequences for Properties of Solids

Abstract

The origin on an atomic scale of huge macroscopic effects of most materials can be subtle. No matter whether a property involves the formation of entire atomic and ionic assembles, supramolecular clusters or inter-phases, their understanding is invariably refined to certain minimal regions. Materials and properties applied and produced by mankind have an immense variety, and a formulation of general rules describing substances of specific types is interesting and timely. Apart from well known thermodynamic, statistical and physical laws, chemical “signposts” toward substances in new groups exhibiting required properties are also needed. The structure-property relations described here focus on hydrogen-bonded structures and their dielectric properties; they pertain to the smallest of atoms and the biological functions of macromolecules and dielectric properties of matter of current interest for technological applications. We show that the spontaneous polarisation in hydrogen-bonded crystals is related to tiny atomic displacements rather than to the largest molecular dipoles present in the structure. New dimensions of the structure-property relations are described for NH+- - -N bonded ferroelectrics and relaxors. The structure-property relations described for hydrogen-bonded crystals are applicable also to substances without hydrogen bonds in other groups