Berlin 2012 – wissenschaftliches Programm
O 63: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles IV (jointly with TT)
O 63.4: Vortrag
Donnerstag, 29. März 2012, 11:30–11:45, HE 101
Unraveling the α-γ phase transition in Ce from first principles — •Marco Casadei1, Xinguo Ren1, Patrick Rinke1, Angel Rubio1, 2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG (TH), Berlin, Germany — 2UPV/EHV, San Sebastian (Fisica Materiales), Spain
The presence of localized, partially occupied f-electron states dictates many of the peculiar physical properties of rare-earth materials. In particular, the description of the isostructural α-γ phase transition in Cerium poses a great challenge to density-functional theory (DFT) based approaches since local/semilocal functionals (LDA/GGA) fail to produce the phase transition. We approach this problem by treating all electrons (including the f-electrons) at the same quantum mechanical level. The calculations are performed using both hybrid functionals (e.g. PBE0), that incorporate a portion of exact-exchange, and full exact-exchange plus correlation at the level of the random phase approximation (EX+cRPA). The PBE0 hybrid functional predicts the correct magnetic properties of both phases and yields a double minimum in the total energy versus volume curve, indicative of the phase transition, although with the wrong energetic order. EX+cRPA is then essential to capture the right energetic ordering of the minima. Our results suggest a hypothetical persistence of the phase transition to zero temperature, the driving mechanism being the change of the hopping amplitude between f-type orbitals.