Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 77: Focus Session: Frontiers of Electronic Structure Theory - Non-Equilibrium Phenomena at the Nano-Scale V (organized by O)
TT 77.8: Vortrag
Mittwoch, 2. April 2014, 18:15–18:30, TRE Ma
Rare Earth Metals in Density-Functional Theory — •Marco Casadei1, Xinguo Ren2, Patrick Rinke1, Angel Rubio1,3, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin — 2University of Technology, Hefei, China — 3NanoBio Spectroscopy group and ETSF, Universidad del País Vasco, San Sebastián, Spain
The presence of f electrons in the rare earths and their interaction with the s and p electrons give rise to several physical phenomena. One prominent example is the isostructural α-γ phase transition in cerium (Ce). We have shown that density-functional theory (DFT) captures the volume collapse associated with the transition, but only if advanced functionals such as exact exchange plus correlation in the random-phase approximation (EX+cRPA) are used [1]. The volume collapse is understood in terms of a localization/delocalization of the f electrons. We then addressed the question: is the isostructural volume collapse in cerium unique? By applying DFT, we studied lanthanum (La), praseodymium (Pr) and neodymium (Nd), which undergo several structural changes with pressure. We find that the transitions are already captured at a lower level of DFT (i.e. with (semi)-local functionals) and therefore conclude that f-electrons are not the driving force in this case. Within hybrid functionals, we find only one phase in lanthanum, which has no f-electrons, and more than one stable solution in the fcc crystal for Pr and Nd, as found for Ce. Unlike in Ce, however, there is always one solution that is the most stable, thus no isostructural volume collapse emerges in agreement with experiments. [1] M. Casadei et al., Phys. Rev. Lett. 109, 14642 (2012).