Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 55: Density functional theory and beyond for real materials II
O 55.5: Vortrag
Mittwoch, 24. März 2010, 16:00–16:15, H34
Bridging rare-earth physics and chemistry: a hybrid functional study for Ce — •Marco Casadei1, Xinguo Ren1, Angel Rubio1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, 14195 Berlin, Germany — 2Dpt. Fisica Materiales, UPV/EHU, San Sebastian Spain
The presence of localized, partially occupied f electronic states is responsible for many peculiar physical properties of rare-earth materials. Of particular interest is the α-γ phase transition in Ce metal, which poses a big challenge to first principles approaches based on local/semilocal (LDA/GGA) approximations to density functional theory (DFT). Within LDA and GGA, the f electrons tend to be more delocalized than they should, and thus the γ phase with localized f electrons can not be described.
Hybrid functionals provide a way of improving the exchange-correlation functionals climbing the so-called Jacob’s ladder in Perdew’s sense to the fourth rung. By incorporating a fraction of exact exchange, hybrid functionals reduce the self-interaction error considerably which is the main reason for the failure of LDA/GGA in this case. It is highly interesting to see how quantitatively hybrid functionals work for this renowned problem. To this end we calculated the cohesive energies of the Ce clusters of increased size, cut from Ce bulk, as a function of the lattice constant. For these clusters, we establish that there exists multi-solution behavior at the hybrid functional (here PBE0) level, which is absent for LDA/GGA. We analyze the implication of this behavior to the α-γ phase in Ce bulk.