An alternative near-neighbor definition of hydrogen bonding in water

A definition of hydrogen bonding in water is proposed in which an H center dot O pair forms a hydrogen bond if (a) an oxygen atom is the nearest nonchemically bonded neighbor of a hydrogen atom; and (b) the hydrogen is the first or the second intermolecular near-neighbor of the oxygen. Unlike the commonly employed hydrogen-bond definitions, this definition does not depend on the choice of geometric or energetic cutoffs applied to continuous distributions of properties. With the present definition, the distribution of O center dot center dot center dot H bond lengths decays smoothly to zero in a physically reasonable range. After correction for the presence of intermittent hydrogen bonds, this definition appears to provide a more stable description of hydrogen bonds and coordination shells than the more conventional cutoff-based definition. "Partial" H bonds satisfying only one of the two bonding requirements serve as transition states in the H-bond network evolution. (c) 2008 American Institute of Physics.