Institute of Applied Physics and Computational Mathematics, China
Haifeng Song has completed his PhD from Tsinghua University. He is Director of research group in the fields of condensed mater physics and material physics. His research interests include the equation of state, phase transition, transport properties of metals, etc. He has published more than 40 papers in reputed journals and has been serving as an Editorial Board Member of repute.
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.