Theoretical estimation of the ionization potential of water in condensed phase. I. Amorphous ice

The possibilities of modern quantum chemical calculations in estimating the physicochemical characteristics of condensed phase specimens, when an increase in the number of particles does not lead to principal changes in the electronic structure, are demonstrated by an example of water, which is the most important solvent in actual corrosion-electrochemical processes. Stationary quantum chemical calculations of (H2O)n water clusters comprising up to 12 molecules and their cations showed that ionization induces the formation of OH and H3O+ fragments. Based on the analysis of the electron density distribution in the systems, a functional dependence of the calculated adiabatic ionization potentials of the clusters on the number of water molecules in them is derived. Extrapolation of this dependence to n → ∞ provides a theoretical estimate of the photoionization threshold of ice.