The role of the lattice in the $\gamma o \alpha$ phase transition of Ce: a high pressure neutron and x-ray diffraction study

摘要

The temperature and pressure dependence of the thermal displacements andlattice parameters were obtained across the $\gamma \to \alpha$ phasetransition of Ce using high-pressure, high-resolution neutron and synchrotronx-ray powder diffraction. The estimated vibrational entropy change per atom inthe $\gamma \to \alpha$ phase transition, $\Delta S^{\gamma - \alpha}_{\rm vib}\approx (0.75 \pm 0.15)$k$_{\rm B}$, is about half of the total entropy change.The bulk modulus follows a power-law pressure dependence which is welldescribed using the framework of electron-phonon coupling. These resultsclearly demonstrate the importance of lattice vibrations, in addition to thespin and charge degrees of freedom, for a complete description of the $\gamma\to \alpha$ phase transition in elemental Ce.