Investigation of the reactions of U, U+ and U2+ with ammonia: mechanisms and topological analysis

Reactions of uranium atom and ions (U, U+ and U2+) with NH3 have been studied in the gas phase using density functional calculations. The detailed description of reaction mechanisms and diverse topological analysis provide insights into the chemistry of uranium species. The reaction pathways leading to different products are closely examined. In the case of U and U+ reacting with NH3, the isomerization channel (the products are H2UNH and H2UNH+, respectively) and H2 elimination channel (decomposed to UNH + H2 and UNH+ + H2) were investigated. In the U2+ + NH3 reaction, UNH2+ was found to be the only product generated by the dehydrogenation of the HUNH22+ intermediate. The obtained results are compared to recent experimental studies. Bonding evolution along with the reactions was investigated using diverse topological analyses, including electron localization function, atoms in molecules, and natural bond orbital. A comparison with other results reported in the literature for similar systems, such as the reactions of uranium species with NH3, H2O and CH4, is made to underline the similarities and differences of the reaction mechanisms.