Multireference F12 coupled cluster theory: The Brillouin-Wigner approach with single and double excitations

►We introduce explicitly correlated multi reference (MR) coupled cluster (CC) method. ► We combine the Brilouin-Wigner MR-CC with the F12 approach with STG. ► The new MR BW-CCSD-F12 approach was tested for H4 model and F2 dissociation. ► Faster convergence towards basis set limit is achieved with MR BW-CCSD-F12.