A theoretical study of the microhydration of iodic acid (HOIO2).

The structures, energetics, and thermodynamic properties of HIO 3 isomers (HOOOI, HOOIO, HOIO 2 , and HIO 3 ) have been computed using CCSD(T)/CBS theoretical method. The spin orbit corrections (SOC) have also been evaluated for the each iodine-containing molecule. The SOC value decreases as the iodine valence increases within the molecule. The results revealed that HOIO 2 was the most stable form and that HOOOI was the next most stable isomer. The standard enthalpies of formation at 298 K have been derived from IO + HO 2 and OH + OIO dissociation pathways. At the CCSD(T)/CBS level on B3LYP geometries, the recommended Δ f H ° 298K is (−95.4 ± 0.3) kJ mol −1 for HOIO 2 , and its computed S ° 298K and C p (300 K) values are respectively 339.12 and 75.28 J mol −1 K −1 . Further, monohydrated and dihydrated complexes of iodic acid have been investigated using DFT and wavefunction methods. Three and six mono- and di-hydrated complexes, respectively, have been identified. The hydrogen bonded complexes (HOIO 2 _1wa and HOIO 2 _2wa) are the lowest lying structures. The thermodynamics of dihydrates have been calculated from the total hydration of iodic acid (HOIO 2 + 2H 2 O). Mono- and di-hydration of iodic acid is a favored process at tropospheric and ambient conditions with the formation of HOIO 2 _1wa and HOIO 2 _2wa at T ⩽ 310 K. The positive Gibbs free energies at high temperatures indicate that gas-phase iodic acid would not be present in a hydrated form inside the nuclear containment building of a pressurized water reactor. [ABSTRACT FROM AUTHOR]