A theoretical study of the microhydration processes of iodine nitrogen oxides

This work reports for the first time the structures and the thermodynamics of the microhydrates of iodine nitrogen oxides (INOx). Monohydrates and dihydrates were investigated for five different INOx species (INO, INO2, cis-IONO, trans-IONO, and IONO2). The structures of the water complexes were characterized at the omega B97XD/aug-cc-pVTZ level of theory. Coupled-cluster calculations were performed with the ANO-RCC-VQZP basis sets. Standard reaction enthalpy and standard Gibbs free reaction energy (Delta(r)G(298 K)(degrees)) were computed for all aggregates. The variation of Delta(r)G(degrees)[T] as a function of temperature reveals that only IONO2 will be hydrated at tropospheric temperatures (T < 270 K). Its dihydration reaction remains a favored process in the same conditions. All INOx species will not be hydrated in gas phase in the containment building of a pressurized water reactor for which temperatures are greater than 400 K.