General Description of Hydrogen-Bonded Solids at Varied Pressures and Temperatures

Abstract

Hydrogen bonds are abundant in Nature. They are intrinsic to the interactions of water molecules and to most of biological substances, cellulose, proteins, DNA strands, or pharmaceutical drugs. Hydrogen bonds are present in numerous minerals in the Earth crust, in water aggregates of water vapour, and in the tiny droplets or ice particles in the clouds. Just like other types of interactions — van der Waals, electrostatic or metallic forces — hydrogen bonds shape the properties of substances, the ability of molecules to form aggregates, to associate with the molecules of other substances, and generally the physical properties of hydrogen-bonded materials. It is due to hydrogen bonds that new branches of chemical sciences have developed, such as supramolecular chemistry or the chemistry of inclusion compounds. In the physical sciences there are several long-studied problems related to hydrogen bonding, such as the transformations of water and ice [1–4] or the paraelectric-ferroelectric phase transition in the KH₂PO₄ and KH₂PO₄-type crystals [5–12]. For a detailed comprehension of the properties of hydrogen-bonded substances it is essential that the structural transformations of hydrogen bonds are classified and understood. Hydrogen bonds are different from other intermolecular interactions because they are directional, and because they involve at least three atoms: the H-atom donor, the H-atom, and the H-atom acceptor. Moreover, there is a considerable variety of different types of hydrogen bonds, between different H-donors and H-acceptors, or those involving two, or more interacting groups, in different environments.