Reaction of CO with UO Nanoclusters.

Adsorption of CO to uranium oxide, (UO), clusters was modeled using density functional theory (DFT) and coupled cluster theory (CCSD(T)). Geometries and reaction energies were predicted for carbonate formation (chemisorption) and Lewis acid-base addition of CO (physisorption) to these (UO) clusters. Chemisorption of multiple CO moieties was also modeled for dimer and trimer clusters. Physisorption and chemisorption were both predicted to be thermodynamically allowed for (UO) clusters, with chemisorption being more thermodynamically favorable than physisorption. The most energetically favored (UO)(CO) clusters contain tridentate carbonates, which is consistent with solid-state and solution structures for uranyl carbonates. The calculations show that CO exposure is likely to convert (UO) to uranyl carbonates.