Density functional theory (DFT) calculations are employed to investigate the full catalytic cycle of CO oxidation by N 2 O on yttrium oxide clusters Y 2 MO 5 (M ¼ Y, Al) in the gas-phase. Extensive structural searches show that both the ground-state structures of Y 3 O 5 and Y 2 AlO 5 contain an oxygen radical (O t c)which plays an important role in CO oxidation. Energy profiles are calculated to determine the reaction mechanisms. Molecular electrostatic potential maps (MEPs) and natural bond orbital (NBO) analyses are employed to rationalize the reaction mechanisms. The results indicate that the whole catalytic cycle for the reaction CO + N 2 O / CO 2 + N 2 , conducted by yttrium oxide clusters Y 2 MO 5 (M ¼ Y, Al), is favored both thermodynamically and kinetically. Moreover, compared with the previous report on di-nuclear YAlO 3 + c and Y 2 O 3 + c, it's obvious we can conclude that tri-nuclear Y 3 O 5 and Y 2 AlO 5 exhibit greatly enhanced catalytic activity toward CO/N 2 O couples.

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Thorium oxide has many important applications in industry. In this article, theoretical calculations have been carried out to explore the hydrolysis reactions of the ThO n (n = 1-3) clusters. The reaction mechanisms of the O-deficient ThO and the O-rich ThO 3 are compared with the stoichiometric ThO 2 . The theoretical results show good agreement with the prior experiments. It is shown that the hydrolysis mainly occurred on the singlet potential surface. The overall reactions consist of two hydrolysis steps which are all favourable in energy. The effects of oxygen content on the hydrolysis are elucidated. Interestingly, among them, the peroxo group O 2 2À in ThO 3 is converted to the HOOÀ ligand, behaving like the terminal O 2À in the hydrolysis which is transformed into the HOÀ groups. In addition, natural bond orbital (NBO) analyses were employed to further understand the bonding of the pertinent species and to interpret the differences in hydrolysis.