Molecular dynamics description of fragmentation

Molecular dynamics of nucleon wave packets, especially the antisymmetrized version of the quantum molecular dynamics, enables us to describe both the mean field dynamics and the cluster formation. It therefore gives us a powerful tool for studying the nuclear dynamics both in the nuclear structure problem and in the nuclear collision problem. In the study of nuclear structure of light nuclei up to the neutron dripline, it presents us with a unique theoretical method which can describe both shell model strucure and the cluster structure and the structure-change between the two. Capability of treating both the mean field dynamics and the dynamical formation of clusters is especially important in the study of heavy ion collisions at intermediate energies because the reaction process is dominated by various types of fragmentation mechanisms. It is shown that the quantum mechanical description is decisive in many respects for studying the fragmentation reaction. One example is the description of the shell effect for the dynamical production of alpha particles. Another example is the channel branching due to the quantum mechanical fluctuation which is indispensable for the multifragmentation. The quantum mechanical channel branching ensures the quantum statistical property of the theory which is indispensable in describing the liquid-gas phase transition of the nuclear system.