Shell model coupled cluster calculation

We present the shell model coupled-cluster calculation of open-shell nuclei. The coupled-cluster method decoupled the reference state. A secondary similarity transformation is applied to the Coupled-cluster effective Hamiltonian to get the valance and excluded space decoupled, which lead to a shell model interaction and is capable to deal with arbitrary number of valance particles. We show that the three-body terms induced by both similarity transformations are crucial for an accurate computation of ground and excited states.