Cluster-shell competition in light nuclei

We demonstrate whether the cluster structure dissolves or remains when the shell-model-like model space is introduced in addition to the cluster model space in light nuclei. Although the binding energies of ⁸Be, ¹⁰Be, and ¹⁰B become larger by about 1--2 MeV by adding shell-model-like basis states to the α+α+N+N+⋯ basis states, the α1000-0ptα structure is a dominant configuration of the ground states. However, α-breaking wave functions strongly mix in ¹²C, and the decrease of the energy from the 3α configuration by about 6 MeV is a clue to resolving a long-standing problem of the binding energies of ¹²C and ¹⁶O. The improved version of antisymmetrized molecular dynamics (AMD), AMD superposition of selected snapshots (AMD triple-S), is used to show the cluster-shell competition of these nuclei.