Phonons of the anomalous element cerium

TitlePhonons of the anomalous element cerium
Publication TypeJournal Article
Year of Publication2011
AuthorsKrisch M, Farber DL, Xu R, Antonangeli D, Aracne CM, Beraud A, Chiang TC, Zarestky J, Kim DY, Isaev EI, Ahuja R, Johansson B
Journal TitleProceedings of the National Academy of Sciences of the United States of America
Date Published06
Type of ArticleArticle
ISBN Number0027-8424
Accession NumberISI:000291341400012
Keywordsalpha-gamma-transition, CE, dynamics, generalized gradient approximation, kondo, LATTICE, volume-collapse

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 gamma-alpha transition in cerium. We have determined by inelastic X-ray scattering, the complete phonon dispersion scheme of elemental cerium across the gamma -> alpha 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 Gruneisen parameters, particularly around the X point. We derive a vibrational entropy change Delta S-vib(gamma-alpha) approximate to (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.

URL<Go to ISI>://000291341400012
Alternate JournalProc. Natl. Acad. Sci. U. S. A.