First-principles study of the high pressure phase transition and lattice dynamics of cerium

We present a first-principles study of the phase transition and lattice dynamics of Ce within the framework of the density functional theory using the GGA+U method. Our calculated results denote that under pressure the transition path is α-Ce (fcc)→α″-Ce (monoclinic, with two atoms per unit cell)→bct-Ce (body centered tetragonal), and the transition pressures are located at 5.36 and 14.37 GPa, respectively. The equation of state in a wide range of pressure is consistent with the experimental data. During the γ–α phase transition, the magnetic moment disappears gradually, which is mainly due to the strong interaction between the 4f and 5d electrons. By calculating the free energies from phonon dispersions including electronic contribution, the obtained γ–α transition temperature at zero pressure is 148 K. From the Blackman diagram of dimensionless elastic constant ratios, we can find that both γ- and α-Ce show negative Cauchy pressure—C44>C12.

Research highlights
► In this work, we present a first-principles study of the phase transition and lattice dynamics of Ce within the framework of the density functional theory using the GGA+U method.
► We clarified the transition path of Ce under pressure; the transition path is α-Ce (fcc)→α″-Ce (monoclinic, with two atoms per unit cell)→bct-Ce (body centered tetragonal), and the transition pressures are located at 5.36 and 14.37 GPa, respectively.
► During the γ–α phase transition, the magnetic moment disappears gradually, which is mainly due to the strong interaction between the 4f and 5d electrons.
► By calculating the free energies from phonon dispersions including electronic contribution, the obtained γ–α transition temperature at zero pressure is 148 K. From the Blackman diagram of dimensionless elastic constant ratios, we can find that both γ- and α-Ce show negative Cauchy pressure—C44>C12.