Density-functional Theory for f electron Systems: the {\alpha}-{\gamma} Phase Transition in Cerium

TL;DR

This paper uses advanced density-functional theory methods to analyze the nd  phase transition in cerium, highlighting the importance of correlation effects in predicting phase stability.

Contribution

It demonstrates how different exchange-correlation functionals affect the prediction of cerium's phase stability, emphasizing the role of correlation in rare-earth systems.

Findings

PBE0 predicts  phase as stable at zero temperature, conflicting with experiments.

EX+cRPA reverses the energetic order, aligning better with experimental observations.

Hartree-Fock exchange induces two solutions corresponding to different phases.

Abstract

The isostructural {\alpha}-{\gamma} phase transition in cerium is analyzed using density-functional theory with different exchange-correlation functionals, in particular the PBE0 hybrid functional and the exact- exchange plus correlation in the random-phase approximation [(EX+cRPA)@PBE0] approach. We show that the Hartree-Fock exchange part of the hybrid functional actuates two distinct solutions at zero temperature that can be associated with the {\alpha} and {\gamma} phases of cerium. However, despite the relatively good structural and magnetic properties, PBE0 predicts the {\gamma} phase to be the stable phase at ambient pressure and zero temperature, in contradiction with low temperature experiments. EX+cRPA reverses the energetic ordering, which emphasizes the importance of correlation for rare- earth systems.