Theoretical atomic volumes of the light actinides

Abstract

The zero-pressure zero-temperature equilibrium volumes and bulk moduli are calculated for the light actinides Th through Pu using two independent all-electron, full-potential, electronic-structure methods: the full-potential linear augmented-plane-wave method and the linear combinations of Gaussian-type orbitalsfitting function method. The results produced by these two distinctly different electronic-structure techniques are in good agreement with each other, but differ significantly from previously published calculations using the full-potential linear muffin-tin-orbital ͑FP-LMTO͒ method. The theoretically calculated equilibrium volumes are in some cases nearly 10% larger than the previous FP-LMTO calculations, bringing them much closer to the experimentally observed volumes. We also discuss the anomalous upturn in equilibrium volume seen experimentally for ␣-Pu.

Ab Initio Enhanced calphad Modeling of Actinide-Rich Nuclear Fuels

“…Such finding is not surprising. In fact, it follows the general trend of DFT-GGA's underestimation of the volume of actinide metals [58]. The trend debatably starts at U, as we have discussed above, and becomes more significant as the atomic number increases-for Np and Pu the calculated volumes are clearly smaller than experimental values even in the most accurate full potential calculations with SOC included (see TABLE I of Ref.…”

“…The trend debatably starts at U, as we have discussed above, and becomes more significant as the atomic number increases-for Np and Pu the calculated volumes are clearly smaller than experimental values even in the most accurate full potential calculations with SOC included (see TABLE I of Ref. [58]). Since the correlation effects become more pronounced with higher atomic number along the actinide series, it is expected that the volume underestimation is due to the correlation effects.…”

Modeling charge self-trapping in wide-gap dielectrics: Localization problem in local density functionals

“…Pierls instability), and systems with weak impurity perturbations. A list (by no means complete) of problematic DFT calculations where an artificial delocalization was reported includes: the hole localization in CaO doped with Li and Na and the F-center in LiF as reported by Dovesi et al 13 ; dimerization in C 4N +2 carbon rings 54 ; the structure of the Al defect in α-quartz 14,15,55 ; exciton selftrappping in presence of thermal disorder 6,56 ; the phase diagram of crystalline Pu (related to a localization of ftype atomic orbitals) 57,58,59 .…”

A high pressure distorted α-uranium (Pnma) structure in plutonium

“…This upturn has been a subject of debate recently. None of the density functional based calculations have so far been able to explain this (see Jones et el [14] and references there in ). Jones et al have attributed this either to the thermal expansion between room temperature and the 0 o K temperature for which band structure calculations have been done or to that the 5f electrons are not fully delocalised in α -Pu.…”