Ab initio investigation of the UO3 polymorphs: Structural properties and thermodynamic stability

Nicholas A. Brincat, Stephen C. Parker, Marco Molinari, Geoffrey C. Allen, Mark T. Storr

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Uranium trioxide (UO3) is known to adopt a variety of crystalline and amorphous phases. Here we applied the Perdew-Burke-Ernzerhof functional + U formalism to predict structural, electronic, and elastic properties of five experimentally determined UO3 polymorphs, in addition to their relative stability. The simulations reveal that the methodology is well-suited to describe the different polymorphs. We found better agreement with experiment for simpler phases where all bonds are similar (α- and δ-), while some differences are seen for those with more complex bonding (β-, γ-, and η-), which we address in terms of the disorder and defective nature of the experimental samples. Our calculations also predict the presence of uranyl bonds to affect the elastic and electronic properties. Phases containing uranyl bonds tend to have smaller band gaps and bulk moduli under 100 GPa contrary to those without uranyl bonds, which have larger band gaps and bulk moduli greater than 150 GPa. In line with experimental observations, we predict the most thermodynamically stable polymorph as γ-UO3, the least stable as α-UO3, and the most stable at high pressure as η-UO3.

Original languageEnglish
Pages (from-to)12253-12264
Number of pages12
JournalInorganic Chemistry
Volume53
Issue number23
Early online date18 Nov 2014
DOIs
Publication statusPublished - 1 Dec 2014
Externally publishedYes

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