Haifeng Song
Institute of Applied Physics and Computational Mathematics, China
Title: The phase transition in cerium metal studied by an LDA+Gutzwiller method
Biography
Biography: Haifeng Song
Abstract
The thermodynamic stable phase of cerium metal in the high pressure regime has been studied by combining density functional theory with the Gutzwiller variational approach (LDA+Gutzwiller), which can include the strong correlation effect among the 4f electrons in cerium metal properly. Our numerical results show that the α″ phase, which has the distorted body-centered-tetragonal structure, is the thermodynamic stable phase in the intermediate pressure regime (5.0-13.0 GPa) and all the other phases including the α′phase (α-U structure), α phase (fcc structure) and bct phases are either metastable or unstable. Our results are quite consistent with the most recent experimental data. We also studied the α-γ iso-structure transition in cerium, we found that the first order transition between α and γ phases persists to the zero temperature with negative pressure. By further providing a newly finite temperature generalization of the LDA+G method (using the mean-field potential approach), the entropy contributed by both electronic quasiparticles and lattice vibration included, we obtain the Gibbs free energy at a given volume and temperature, from which we get the α-γ transition at finite temperature and pressure. Our results indicate that the electronic entropy and lattice vibrational entropy both play important roles in the α-γ transition. We also calculated the equation of state and phase diagram of cerium, finding good agreement with the experiments.