Recently, the symmetry-adapted perturbation theory (SAPT) first-order exchange term was extended to low-spin complexes resulting from the interaction of high-spin open-shell monomers by way of the spin-flip electronic structure formalism. This talk describes the next step in the development of the resulting spin-flip SAPT (SF-SAPT), specifically the production of an improved expression for the first-order exchange energy that forgoes the common single exchange approximation of SAPT and replaces it with a single spin flip approximation. To derive the complete exchange term, it is seen that the single spin flips can be treated as a specific subset of the double excitations needed for the calculation of the second-order exchange-dispersion term. The new expressions can be seen to go beyond the Heisenberg Hamiltonian description of the previous method. This new methodology is tested on a selection of small systems to gauge the effect of removing the single exchange approximation, then applied to the determination of the singlet-triplet splitting of several larger pancake-bonded complexes.

Spin splittings from first-order symmetry-adapted perturbation theory without the single exchange approximation

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.