# Berlin 2012 – wissenschaftliches Programm

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# O: Fachverband Oberflächenphysik

## 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 Casadei^{1}, Xinguo Ren^{1}, Patrick Rinke^{1}, Angel Rubio^{1, 2}, and Matthias Scheffler^{1} — ^{1}Fritz-Haber-Institut der MPG (TH), Berlin, Germany — ^{2}UPV/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.