Charge distribution and local structure and speciation in the UO2+x and PuO2+x binary oxides for x⩽0.25

XAFS measurements indicate that, for both UO2.25 and PuO2.25, the oxidation of the AnO2.00 starting material results in the formation of actinyl, An-oxo groups, concomitant with additional lattice distortions involving both the O and An sites .