Ab initio multireference in-medium similarity renormalization group calculations of even calcium and nickel isotopes

We use the newly developed multireference in-medium similarity renormalization group to study all even isotopes of the calcium and nickel isotopic chains, based on two- plus three-nucleon interactions derived from chiral effective field theory. We present results for ground-state and two-neutron separation energies and quantify their theoretical uncertainties. At shell closures, we find excellent agreement with coupled-cluster results obtained with the same Hamiltonians. Our results confirm the importance of chiral 3N interactions to obtain a correct reproduction of experimental energy trends, and their subtle impact in neutron-rich Ca and Ni isotopes. At the same time, we uncover and discuss deficiencies of the input Hamiltonians which need to be addressed by the next generation of chiral interactions.