Role of the Lattice in the γ → α Phase Transition of Ce: A High-Pressure Neutron and X-Ray Diffraction Study

摘要

The temperature and pressure dependence of the thermal displacements and lattice parameters were obtained across the γ → α phase transition of Ce using high-pressure, high-resolution neutron and synchrotron x-ray powder diffraction. The estimated vibrational entropy change per atom in the γ → α phase transition, ΔS_(vib)~(γ―α)≈(0.75 +- 0.15)k_B, is about half of the total entropy change. The bulk modulus follows a power-law pressure dependence that is well described using the framework of electron-phonon coupling. These results clearly demonstrate the importance of lattice vibrations, in addition to the spin and charge degrees of freedom, for a complete description of the γ → α phase transition in elemental Ce.