Development of a relativistic 4-component multi-reference coupled cluster method

We present the generalization of the multi-reference coupled cluster (MRCC) method as initially implemented by Olsen to the relativistic framework where spin-orbit interaction is included. The current implementation is partially based on configuration interaction expansions where optimal scaling of the method is not ensured. An extension to a commutator-based implementation with optimal scaling is in progress. The current program, however, surpasses available relativistic MRCC approaches in that it call correctly describe molecular ground states with multi-reference character and an arbitrary number of impaired electrons, and that it can treat arbitrary excitation levels. The program is implemented within a local version of the DIRAC program package, and we sketch initial applications.