The adiabatic connection fluctuation-dissipation theorem (ACFDT) formulation of density func- tional theory (DFT) seamlessly connects time-dependent DFT to the computation of the ground state correlation energy in many-electron systems. The random phase approximation (RPA), the most popular variant of the ACFDT in use today, has proven to be superior to semi-local density functionals for prediction of thermochemistry, weak interactions, and structural properties for molecules and materials alike.1,2 RPA has even been shown to mimic static-correlation through its self-correlation error3, which leads to more accurate barrier heights and kinetic predicitions compared to semi-local methods and hints at RPA’s ability to perform even for “more strongly correlated” systems. To understand the performance of RPA for strongly-correlated chemistry, the asymmetric Hubbard dimer (molecule) has been investigated using the exact adiabatic-connection to compare with approximate ACFDT methods. The ability of RPA to deliver a reasonable starting point for renormalized, perturbative corrections from the Bethe-Salpether equation across various ratios of the asymmetry to the on-site repulsion will be discussed, and the results compared to approximations beyond RPA involving the formally exact, frequency-dependent, exchange-correlation kernel.4

Adiabatic-connection analysis of RPA correlation in the asymmetric Hubbard dimer

2019 Spring National Meeting

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