A model potential approach to charge resonance phenomena in aromatic cluster ions

This work proposes a simple yet accurate methodology to account for charge resonance in ionic clusters. The supersystem's model Hamiltonian is described via a basis set of valence bond structures for which the charge is localized on a given monomer, and whose intermolecular binding energies are computed using a polarizable model potential. The coupling elements between these structures are proportional to an overlap integral between relevant nonorthogonal monomer molecular orbitals. Ab initio calculations are employed to calibrate and validate the model, but also to define its limits. The methodology is then applied to the global exploration of potential energy surfaces for small homocluster ions of benzene, naphthalene, and anthracene. The structural and electronic properties of these systems are discussed, with emphasis on important trends such as the polarization vs charge-transfer competition or the difference between adiabatic and vertical ionization potentials. Extensions to stacked cluster ions of higher aggregation number (n = 15) conclude this work.