The dominant x-rayscattering arises from plutonium, indicating that the plutonium lattice positions remain essentially unchanged. This new material, possessing plutonium with an overall valence greater than (IV)-PuO 2+x, has unit cell dimensions scarcely increased over those of PuO 2-5.404 angstroms () versus 5.3975 -in spite of the suggested placement of the extra oxide ion at body center, enclosed by the close-fitting subcell of eight oxide ions.

(This will be explained in depth in the following articles.)

Experimental data using x-ray absorption near edge structure (XANES) and x-ray photoelectron spectroscopy (XPS) unequivocally demonstrate that the PuO 2+x entity has plutonium(V) in the structure. Alternatively, one could spread the charge over two plutonium core atoms in the unit cell and arrive at Pu 2 5+Pu 2 4+O 9, or possibly spread the charge over the entire unit cell core so that each plutonium atom that shares the charge is balanced equally with an average plutonium valence of +4.5. One obvious way is to assign one plutonium atom a valence state of (VI). There are several ways to achieve charge balance over the unit cell. We propose replacing the central oxide in Pu 4O 9 with hydroxide, yielding Pu 4O 8OH. 301, July 25, 2003, and described in the previous article, is drawn with strictly oxygen ions, yielding a unit cell composition of Pu 4O 9. This structure, proposed in a report, 'First-Principles Calculations of PuO 2±x,' that appeared in Science, Vol. Oxygen atoms are shown in red, and plutonium in black.Ī structure that purportedly contains all the salient features of the PuO 2+x entity is the unit cell description of PuO 2 with an added oxygen ion in the center of the structure. The molecular structure of plutonium dioxide (PuO 2) with an added oxygen ion (yellow) in the center. (Later articles will discuss the crucial role of water.) That the material can be prepared in a nominal oxidation state higher than plutonium(IV) using water as an oxidant is especially puzzling. This finding is profound in that all other attempts to produce a binary oxide of plutonium with a higher valence have failed.

The importance of this finding is that plutonium dioxide is suggested to oxidize above a plutonium valence state of (IV) with a commensurate weight gain in the solid material. The composition of the resulting fluorite-related solid phase was described as PuO 2+x with x=0.265 as the oxygen increase limit. The preceding article described how, at temperatures of 50 to 350 degrees Celsius, the reaction of plutonium dioxide (PuO 2) with water yielded hydrogen gas and increased oxygen content in the solid. Proposing a hydroxide ion, rather than a central oxide ion, The Actinide Research Quarterly: 2nd Quarter 2004 contents

Oxygen charge of ion