  Exchange coupling constants ($J$) are fundamental to the understanding of
spin spectra of magnetic systems. Here we investigate the broken-symmetry (BS)
approaches of Noodleman and Yamaguchi in conjunction with coupled cluster (CC)
methods to obtain exchange couplings. $J$ values calculated from CC in this
fashion converge smoothly towards the FCI result with increasing level of CC
excitation. We compare this BS-CC scheme to the complementary EOM-CC approach
on a selection of bridged molecular cases and give results from a few other
methodologies for context.
