Microscopic characteristics of hydrogen bonds of hydrated borates

A lot of confusion still exists in employing hydrogen bonds in chemical research, though hydrogen bond research has strongly expanded in depth as well as in breadth in recent years. From our previous studies, it is found that hydrogen bonds are of particular interest in the study of the structure-property relationship of functional crystals. In this work, the microscopic characteristics of homonuclear O-H⋯O hydrogen bonds in crystals are reconsidered. On the basis of the idea that hydrogen bonds consist of two types of bonds, the stronger O-H and weaker H⋯O bonds are, for the first time, considered to have different bond-valence parameters d0S and d0W, respectively. According to the electrostatic equilibrium distribution of the only one valence electron of the hydrogen cation, Coulomb's Law is applied to associate with the bond-valence sum (BVS) model. The parameters d0S and d0W are obtained via a comprehensive survey of crystal structures of more than 100 hydrated borates with the H+ positions available in the Inorganic Crystal Structure Database (2004). The validity of two fitted linear equations, where the parameter d0 is directly related to the respective bond length, indicates that the novel idea treating the parameter d0 provides us a useful way to structurally design new type hydrated borates, even for other non-borate functional materials.