Ab initio calculations of the hydrogen bond

Recent x-ray Compton scattering experiments in ice have provided useful information about the quantum nature of the interaction between H$_2$O monomers. The hydrogen bond is characterized by a certain amount of charge transfer which could be determined in a Compton experiment. We use ab-initio simulations to investigate the hydrogen bond in H$_2$O structures by calculating the Compton profile and related quantities in three different systems, namely the water dimer, a cluster containing 12 water molecules and the ice crystal. We show how to extract estimates of the charge transfer from the Compton profiles.Comment: 16 pages, 7 figures, to appear in Phys. Rev.

INFLUENCE OF THE HYDROGEN BONDING ON THE ULTRAVIOLET SPECTRA OF ORGANIC MOLECULES AN ELECTRONIC THEORY

Author Institution: Centre de M\'ecanique Ondulatiore Appliqu\'ee“An electronic theory in presented explaining the influent of a hydrogen bond on the ultraviolet spectra of organic molecules. The complexes formed by hydrogen bonds are considered as separate units independently of the rest of the solvent molecules and are treated, for a number of molecules, by the Pariser-Parr-Pople procedure. The conclusions which can be drawn from this study are the following ones: a) The perturbations caused by a hydrogen bond on the $n \rightarrow \pi^{*}$ and $\pi \rightarrow \pi^{*}$ bands are due, essentially, to the transfer of the $\sigma$-electrons resulting from the hydrogen bond formation. In spit of the fact that this perturbation acts in a very different way in proton donor and in proton acceptor molecules, the calculated shifts of the $\pi \rightarrow \pi^{*}$ bands are bathochromic in both cases. b) These perturbations are essentially of an inductive type. It is therefore useful to compare the influence of a hydrogen bond to that of a weak inductive substituent. c) The configuration interaction effects are important in many cases.