Molecular charge distribution and charge fluxes from Atomic Polar Tensors: The case of OH bonds

An analytical model based on the Equilibrium Charges and Charge Fluxes (ECCF) theory is presented for the determination of the molecular charge distribution and its mobility on the basis of the Atomic Polar Tensors obtained by first-principles calculations. The case of OH bonds in molecules containing the >COH and COOH functional groups are analyzed in details and explicit equations are reported for the straightforward calculation of equilibrium atomic charges and charge fluxes. The values obtained describe correctly the intramolecular properties and show a good transferability among similar molecules. The model can be applied not only to the interpretation of the peculiar chemical/physical properties of functional groups in their specific intramolecular environment, but it can be also used as a theoretical method to investigate the effect of the molecular charge distribution and its mobility on IR absorption intensities, i.e. the correlation between ECCF and experimentally measurable quantities.