Comparison of bonding and charge density inδ−UO3,γ−UO3, andLa6UO12

Abstract

This computational paper examines the effect of local atomic environments on the electron charge density in $\ensuremath{\delta}\text{\ensuremath{-}}\mathrm{U}{\mathrm{O}}_{3},\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{U}{\mathrm{O}}_{3}$, and $\mathrm{L}{\mathrm{a}}_{6}\mathrm{U}{\mathrm{O}}_{12}$. In particular, this paper reveals differences in the uranium local atomic environments in these model oxide compounds. To examine the differences in a quantitative way, atoms-in-molecule (AIM) and Bader analysis methods were used to interrogate the electron charge density. The electron charge-density distribution in each compound was obtained using density functional theory. The AIM-Bader analyses provided estimates for the so-called Bader charges on individual lattice atoms, as well as the locations of the bond critical points (BCPs) between bonding atoms and the charge densities at the BCPs. Calculation results revealed a quantitative inverse correlation between the charge density at the BCP and the U-O bond length. In addition, this inverse correlation was found to be surprisingly similar to a well-established crystal chemical relationship between bond strength and bond length.