Ground- and excited-state properties of hydrogen-bonded water monomers studied by first-principles calculations

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We plan to study the relation and interplay between the structural properties of aggregated water molecules and their electronic and optical excitations. In particular, we want to clarify the optical fingerprints and electronic excitation spectra of one-, two-, three-, and four-fold hydrogen-bonded water monomers in dependence on the surrounding matrix. To that end, calculations are performed for water clusters and one-dimensional water chains in the gas-phase, bulk structures that model solid and liquid water as well as point defects and surfaces of solid water. The analysis of the calculated spectra in comparison with experiment is expected to help significantly to resolve the controversy on the structural properties of liquid water and in understanding the localisation characteristics of hydrated electrons. The proposed calculations proceed in three steps: (i) Atomic and electronic ground-state properties are obtained from density-functional theory calculations within the generalised gradient approximation to describe exchange and correlation. (ii) The electronic self-energy is included on the level of the GW approximation and (iii) electron-hole attraction effects are determined on the basis of an initial-value formulation of the Bethe-Salpeter equation.