The heavy-ion fusion reactions with 16O bombarding on 62Ni, 65Cu, 74Ge, 148Nd, 180Hf, 186W, 208Pb, 238U are systematically investigated with the improved quantum molecular dynamics (ImQMD) model. The fusion cross sections at energies near and above t
he Coulomb barriers can be reasonably well reproduced by using this semi-classical microscopic transport model with the parameter sets SkP* and IQ3a. The dynamical nucleus-nucleus potentials and the influence of Fermi constraint on the fusion process are also studied simultaneously. In addition to the mean field, the Fermi constraint also plays a key role for the reliable description of fusion process and for improving the stability of fragments in heavy-ion collisions.
The heavy-ion fusion reactions induced by neutron-rich nuclei are investigated with the improved quantum molecular dynamics (ImQMD) model. With a subtle consideration of the neutron skin thickness of nuclei and the symmetry potential, the stability o
f nuclei and the fusion excitation functions of heavy-ion fusion reactions $^{16}$O+$^{76}$Ge, $^{16}$O+$^{154}$Sm, $^{40}$Ca+$^{96}$Zr and $^{132}$Sn+$^{40}$Ca are systematically studied. The fusion cross sections of these reactions at energies around the Coulomb barrier can be well reproduced by using the ImQMD model. The corresponding slope parameter of the symmetry energy adopted in the calculations is $L approx 78$ MeV and the surface energy coefficient is $g_{rm sur}=18pm 1.5$ MeVfm$^2$. In addition, it is found that the surface-symmetry term significantly influences the fusion cross sections of neutron-rich fusion systems. For sub-barrier fusion, the dynamical fluctuations in the densities of the reaction partners and the enhanced surface diffuseness at neck side result in the lowering of the fusion barrier.
The pre-neutron-emission mass distributions for reaction $^{238}$U(n, f) up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependence of the peaks and valleys of the pre-neutron-emission mass distributions
is described by an exponential form based on the newly measured data. The energy dependence of evaporation neutrons before scission is also considered, which plays a crucial role for the reasonable description of the mass distributions. The measured data for the pre-neutron-emission mass distributions for reaction $^{238}$U(n, f) are reasonably well reproduced up to 60 MeV. The mass distributions at unmeasured energies are also predicted with this approach.
Finite size effect on the antiferromagnetic transition temperature, TN, of Co3O4 nanoparticles of 75, 35, and 16 nm in diameter, has been investigated. The AFM transition point, TN, reduces with the decreasing diameter, d. Along with the results from
the previous experiments on the Co3O4 nanoparticles of 8 and 4.3 nm, the variation of TN with d appears to follow the finite size relation. According to the scaling behavior, the shift exponent is determined as lambda = 1.4 pm 0.4, the correlation length, ksi_0 = 3.0 pm 0.3 nm, and the bulk Neel temperature, TN(infint) = 38.6 pm 0.7 K.
