Quantum simulations and a b i n i t i o electronic structure studies of (H2O)−2

Abstract

The energetics of the negatively charged water dimer (H₂O)⁻₂, is studied using quantum‐simulation techniques and ab initio electronic structure calculations. Using the RWK2‐M potentials for water and a pseudopotential for the interaction of an electron with a water molecule in the ground state, consisting of Coulomb, adiabatic polarization, exclusion, and exchange contributions, it was found via the quantum path‐integral molecular dynamics and the coupled quantum‐classical time‐dependent self‐consistent field methods that while the minimum energy of (H₂O)⁻₂ corresponds to a nuclear configuration similar to that found for the neutral (H₂O)₂ cluster, other nuclear configurations are also exhibited at finite temperature, characterized by a higher total molecular cluster dipole moment and a larger magnitude of the excess electron binding energy. Quantitative agreement is found between the results obtained by the quantum simulations, employing the excess electron–molecule pseudopotential, and those derived, for selected nuclear configurations, via ab initio calculations, employing the Gaussian 86 code with the basis set for the water molecules supplemented by a large diffuse set located at the midpoint of the two oxygens and in addition by a diffuse set for the excess electron.