Relativistic DMRG-based externally corrected coupled cluster methods

Since its invention in solid state physics, the density matrix renormalization group (DMRG) method has proven itself as a powerful method for description of strongly correlated systems. In the last decade, it has also been successfully applied in quantum chemistry, where it has become a method of choice for strongly multiconfigurational systems. It has been implemented also in the relativistic 4-component formalism to handle molecules containing heavy atoms. Nevertheless, to achieve the ``chemical accuracy'', its lack of description of the dynamic correlation is a serious drawback. We suggest to exploit the information from the relativisti DMRG method to externally correct relativistic single- and multi-reference coupled cluster methods and include thus the remaining dynamic correlation. Our recent work has shown that this scheme gives promising results in the non-relativistic regime and we would like to extend its applicability to heavy atoms by implementing it in the relativistic form.