A general hydrogen bonding definition based on three-dimensional spatial distribution functions and its extension to quantitative structural analysis of solutions and general intermolecular bonds

J Dockal and M Svoboda and M Lisal and F Moucka, JOURNAL OF MOLECULAR LIQUIDS, 281, 225-235 (2019).

DOI: 10.1016/j.molliq.2019.02.036

Numerous microscopic definitions of hydrogen bonding have been proposed and employed in molecular simulations. They are typically based on various energetic, topological, and geometric criteria and require a specification of the cut-off values. The cut-off values are chosen to yield a reasonable description of hydrogen bonding in a particular molecular system under particular conditions and for a particular molecular model, and they are not thus straightforwardly transferable to different molecular systems or conditions. We propose a general approach to define and quantify the intermolecular bonds in liquids and solutions, including hydrogen bonds, which is free of any cutoff values. The approach is based on finding a continuous bond region in the surroundings of a local maximum of a spatial distribution function, enclosed by an isosur-face going through the nearest significant saddle point. Moreover, the general definition of intermolecular bonding can quantify significance of particular intermolecular bonds or can be used locally to quantify and characterise bonds in heterogeneous systems or confinement. Besides the general definition of the intermolecular bonding, the bond region can be further characterised by a number of relevant properties such as the number of bonds per molecule, volume of a bond region per molecule, bond stability/strength or hydration number to provide deep insight into the intermolecular bonding. The approach is demonstrated for pure water and aqueous NaCl solutions under different thermodynamic conditions, and our results on the behaviour and quantification of their intermolecular bonding are compared with results obtained using commonly-used bond definitions. (C) 2019 Elsevier B.V. All rights reserved.

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