Isospin effects on collective flow in HIC at intermediate energies

Based on an isospin-dependent quantum molecular dynamics model, the neutron and proton density calculated from Skyrme-Hartree-Fock theory, along with the neutron and proton Fermi momenta calculated from Fermi gas model, are used to sample stable initial nuclei, Fe-58 and Ni-58. The isospin effects on collective flow in reaction systems 55MeV / u Fe-58 + Fe-58 and 55MeV / u Ni-58 + Ni-58 are studied in detail. At different impact parameters for different types of fragments, it is shown that the neutron-rich system Fe-58 + Fe-58 has stronger collective flow than the system Ni-58 + Ni-58, which could qualitatively agree with the results of the experiments. Meanwhile, the effects of both isospin-dependent symmetry energy and nucleon-nucleon cross sections on collective flow are studied.