Microscopic study of neutron-induced fission process of ²³⁹Pu via zero- and finite-temperature density functional theory*

Abstract

To study the neutron-induced fission of $^{239}$Pu, the potential energy surfaces (PESs) calculations have been performed by the zero and finite-temperature density functional theory (FT-DFT) with the Skyrme force. The changes of the least-energy fission path, the fission barrier, total kinetic energy (TKE), the scission line and mass distribution of fission fragments with the incident neutron energy are analyzed. Two different ways have been used to calculate the fission yields of the neutron-induced fission $^{239}$Pu(n,f) with different incident neutron energies, in the framework of time-dependent generator coordinate method (TDGCM). One way to calculate the fission yield of $^{239}$Pu(n,f) is to solve the collective equation of TDGCM by using the PES from the FT-DFT with the corresponding temperature. The other is using the PES from the zero-temperature DFT but adjusting the initial collective energy of the wave packet in the TDGCM to the incident neutron energy. For the cases of the lower incident neutron energies, these two methods give similar results, and could reproduce the experimental peak and width of fission fragment distribution. However, for the highest incident neutron energy considered in this study, the results from the TDGCM by using the PES from zero-temperature DFT deviate explicitly to the experimental data, but those by using the PES from TD-DFT are still close to experimental data. It might be regarded as a proof that with the increase of the incident neutron energy, the shell structure of the compound nuclei has changed explicitly so that it may not be proper to use the same PES from zero-temperature to do the fission dynamic calculation.