title: Phonons of the anomalous element cerium.
abstract: Many physical and chemical properties of the light rare-earths and actinides are governed by the active role of f electrons, and despite intensive efforts the details of the mechanisms of phase stability and transformation are not fully understood. A prominent example which has attracted a lot of interest, both experimentally and theoretically over the years is the isostructural γ - α transition in cerium. We have determined by inelastic X-ray scattering, the complete phonon dispersion scheme of elemental cerium across the γ → α transition, and compared it with theoretical results using ab initio lattice dynamics. Several phonon branches show strong changes in the dispersion shape, indicating large modifications in the interactions between phonons and conduction electrons. This is reflected as well by the lattice Grüneisen parameters, particularly around the X point. We derive a vibrational entropy change ΔS(γ-α)(vib) ≈ (0.33+/-0.03)k(B), illustrating the importance of the lattice contribution to the transition. Additionally, we compare first principles calculations with the experiments to shed light on the mechanism underlying the isostructural volume collapse in cerium under pressure.
authors: European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Cédex, France.
authors: Michael
authors: M
authors: Krisch
authors: D L
authors: DL
authors: Farber
authors: R
authors: R
authors: Xu
authors: Daniele
authors: D
authors: Antonangeli
authors: C M
authors: CM
authors: Aracne
authors: Alexandre
authors: A
authors: Beraud
authors: Tai-Chang
authors: TC
authors: Chiang
authors: J
authors: J
authors: Zarestky
authors: Duck Young
authors: DY
authors: Kim
authors: Eyvaz I
authors: EI
authors: Isaev
authors: Rajeev
authors: R
authors: Ahuja
authors: Börje
authors: B
authors: Johansson
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