Coupled-Cluster Calculations for Ground and Excited States of Closed- and Open-Shell Nuclei Using Methods of Quantum Chemistry

We discuss large-scale ab initio calculations of ground and excited states of 16O and preliminary calculations for 15O and 17O using coupled-cluster methods and algorithms developed in quantum chemistry. By using realistic two-body interactions and the renormalized form of the Hamiltonian obtained with a no-core G-matrix approach, we are able to obtain the virtually converged results for 16O and promising results for 15O and 17O at the level of two-body interactions. The calculated properties other than binding and excitation energies include charge radius and charge form factor. The relatively low costs of coupled-cluster calculations, which are characterized by the low-order polynomial scaling with the system size, enable us to probe large model spaces with up to seven or eight major oscillator shells, for which nontruncated shell-model calculations for nuclei with A = 15–17 active particles are presently not possible.