Theoretical study on electron-phonon coupling factor and electron-ion nonequilibrium process in uranium

Rapid laser heating is an important experimental technique to achieve extreme conditions for uranium. Theoretical simulations of the electron-ion nonequilibrium energy relaxation after laser heating usually employ a two-temperature model using the thermal quantities of the electron heat capacity and the electron-phonon coupling factor as input parameters. Based on the first-principles calculations of the electron density of states and Eliashberg function, we theoretically determine the thermal quantities and their dependence on electron temperature and external pressure for uranium and revealed the connection between the thermal quantities and the electron density of states. The electron/ion temperature evolution was examined by employing the two-temperature model with the obtained thermal quantities. The time/temperature at the peak/equilibrium point of the temperature evolution curve was examined for different external pressures and different laser energy densities. We found that the approximation of a linear temperature-dependent electron heat capacity is acceptable at a low energy density, while at a high energy density, the electron temperature dependence of the electron heat capacity and the coupling factor from the first-principles calculations must be considered.National Natural Science Foundation of China (NSFC) [11504025, 11475031, 11274019, 11275032]; NSAF Foundation [U1530113, U1530258]; foundation of President of Chinese Academy of Engineering Physics [2014-1-036]; foundation for Development of Science and Technology of China Academy of Engineering Physics [2014B0301053]SCI(E)ARTICLE22