Nonmagnetic and ferromagnetic fcc cerium studied with one-electron methods

Abstract

Density functional theory was used to study the nonmagnetic (NM) and ferromagnetic (FM) phases of face-centered cubic cerium. Functionals of four levels of approximations for the exchange-correlation energy were used: LDA, PBE, LDA/PBE+$U$, and YS-PBEh. The latter two contain an adjustable parameter, the onsite Coulomb repulsion parameter $U$ for LDA/PBE+$U$ and the fraction $\alpha_x$ of Hartree-Fock exchange for YS-PBEh, which were varied in order to study their influence on the results. By supposing that, as a first approximation, the NM and FM solutions can be identified to the observed $\alpha$ and $\gamma$ phases, respectively, it is concluded that while a small value of $U$ or $\alpha_x$ leads to the correct trend for the stability ordering of the two phases, larger values are necessary for a more appropriate (but still not satisfying) description of the electronic structure.