PBE+Ucalculations of the Jahn-Teller effect inPrO2

Abstract

The Jahn-Teller distortion in praseodymium dioxide $(\mathrm{Pr}{\mathrm{O}}_{2})$ has been studied using density functional theory with the $\mathrm{PBE}+U$ functional for the exchange-correlation energy. Various possible distortions were suggested based on recent neutron diffraction experiments [C. H. Gardiner et al., Phys. Rev. B 70, 024415 (2004)]. We could identify the most likely distorted structure with a magnitude of the distortion in very good agreement with the experiment. This structure is the one with the lowest total energy and the corresponding calculated electronic and magnetic properties agree well with the experiment. We investigated the dependency of various properties on the Coulomb parameter ${U}_{\mathrm{eff}}=U\ensuremath{-}J$ and suggest ${U}_{\mathrm{eff}}=6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ as the most appropriate value, for which about 1.65 $4f$ electrons (one localized plus 0.65 delocalized) per Pr atom are found. We also show that magnetism (antiferromagnetism or ferromagnetism) has only a minor influence on the energy and magnitude of the distortion, which is consistent with the fact that the N\'eel temperature $(13.5\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ is much smaller than the temperature of $120\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ below which the distortion is observed.