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Abstract

In this work, we propose to use In-Medium Similarity Renormalisation Group (IMSRG) scheme to study the precise structure of atomic systems with a Dirac-Hartree Fock (DHF) reference frame. IMSRG was developed as a many-body method in the field of nuclear physics to decouple degrees of freedom in highly correlated Hamiltonians. DHF, on the other hand, is a well-established meanfield approach in the field of atomic physics where relativistic effects for multi-electron species are calculated using a mean-field potential. Precise agreement with experiment and prediction power are essential in the field of atomic physics. In this work, we provide a way to combine these two methods to accurately calculate ground states of atomic systems. We provide calculations comparable to state-of-the-art benchmarks for closed shell atomic systems and some proof-of-concept calculations for open shell atoms which have so far eluded most ab-initio methods in the field. We also address some key limitations of our method and outline steps needed to overcome them.