The importance of high temperature electron-phonon coupling to the thermodynamic properties of Ce_0.9Th_0.1 and other f-electron bonded metals

Recent results from inelastic neutron scattering studies on Ce _0.9Th_0.1 are used to demonstrate the importance of electron-phonon coupling to the physical properties of f-electron bonded metals. In the case of Ce_0.9Th_0.1, the phonon density of states (DOS) of α-phase shows a significant softening when heated but shows no change across the α-γ transition despite the 11% volume change. This is supported by analysis of the magnetic spectra showing that most of the transition entropy can be accounted for with the crystal field and spin fluctuations. The precursor phonon softening, the lack of any phonon change across the transition, the magnetic spectra, and the volume transition itself can all be explained in terms of the atomic displacement sensitivity of the hybridization of the local f-electrons with conduction electrons. The electron-phonon coupling resulting from these displacement-sensitive electronic states appears to be essential to understanding cerium. Some of the behavior characteristic of these states, a large volume changes and precursor phonon softening, occurs in many other f-electron bonded metals suggesting that the phenomena is not unique to cerium.