The Fermi Constraint In Quantum Molecular Dynamics Model

The microscopic dynamics simulations of heavy-ion collisions （HICs） are impor-tant not only for the study of multi-fragmentation process at intermediate energies but also for the study of fusion reactions at energies near Coulomb barrier. One of the hot topics in Nuclear physics is to develop a reliable microscopic dynamics model to simu-late the heavy-ion collisions at low and intermediate energies, Study dynamics mecha-nism of reaction, and make it clear that the best partner of projectile-target combination and incident energy to synthesize the new neutron-rich nuclide.As a semi-classic microscopic dynamics transport model, the quantum molecular dynamics（QMD） model is wodely used in the study of heavy-ion collision. By consid-ering momentum redistribution via two-body elastic scattering in the Fermi constrain-t procedure, the fermion properties and the stability of the model can be effectively improved, But with this constraint, the improvement on the high momentum part of momentum distribution is not obvious. In order to further improve the stability of the model, The Fermi constraint procedure is modified and the momentum transfer in the momentum re-distribution process is simultaneously considered in addition to the’e-lastic scattering’. the stability of the initial nuclei and fragments produced in heavy-ion collisions can be further improved in the quantum molecular dynamics simulations. The case of the phase space occupation probability larger than one is effectively re-duced with the proposed procedure. Simultaneously, the energy conservation can be better described for both individual nuclei and heavy-ion reactions, and the improve-ment of the fermion properties can significantly reduce the number of spurious emitted nucleons.With the revised version of the improved quantum molecular dynamics （ImQMD） model, the fusion excitation functions of ¹⁶O+¹⁸⁶W and the central collisions of ¹⁹⁷Au+¹⁹⁷Au at 35 AMeV are re-examined. The fusion cross sections at sub-barrier energies and the charge distribution of fragments are relatively better reproduced due to the reduction of spurious nucleon emission.The charge and isotope distribution of fragments in ¹²⁹Xe+¹²⁰Sn,²³⁸U+²³⁸U and ⁹⁶Zr+¹²⁴Sn at intermediate energies are also predicted. More unmeasured extremely neutron-rich fragments with Z=16-28 are observed in the central collisions of ²³⁸U+²³⁸U than that of ⁹⁶Zr+¹²⁴Sn, which indicates that multi-fragmentation of U+U may offer a fruitful pathway to new neutron-rich isotopes.In addition, with the ImQMD-v2.2 model, the deep inelastic scattering process in ¹⁵⁴Sm+¹⁶⁰Gd at nearly-barrier energies is studied. We found that two differen-t microscopic dynamics model TDHF and ImQMD give the similar predictions:no fusion process is observed, Deep inelastic scattering is dominant at central collisions. By estimating the interaction potential between two nuclei, the capture pocket in the nucleus-nucleus potential completely disappears.