Electronic structure of ionized noncovalent dimers

PHYS 198

Anna I. Krylov, krylov@usc.edu, Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482
Electronic structure of the benzene dimer cation is characterized by EOM-CC methods and interpreted in terms of dimer molecular orbitals - linear combination of fragment molecular orbitals model. From the electronic structure point of view, ionization of a van der Waals dimer changes formal inter-fragment bond order from zero to half-integer and, therefore, switches the interaction from non-covalent to covalent. Ionization from an anti-bonding orbital results in a bound electronic state, whereas ionization from bonding orbital - in a dissociative one. In the benzene dimer, additional complexity arises due to degeneracies of monomers' MOs.