Explicitly correlated multireference coupled cluster methods

Abstract: The aim of this project is to develop explicitly correlated (R12/F12) multireferencecoupled cluster methods by merging the R12/F12 techniques employed so far in thesingle-reference coupled cluster field with the Hilbert-space multireference CC approaches. The resulting methods should combine the advantages of explicitly correlated methods in description of the dynamic electron correlation with theability of multireference methods to describe the static correlation.In the first step we should be concerned with the simpler Brillouin-Wigner MRCC approach, then approch the exactly size-extensive Mukherjee MRCC variant,which has more complicated form of coupling terms. The resulting computerimplementation will be used for study of diradicals, bond breaking etc., both for the purpose of assessment of the newly developed methods and forobtaining new results on chemically interesting systems, not accessible previously with a comparable accuracy.