Theoretical study on microhydration of NO3- ion: Structure and polarizability

Graphical abstract: Both static and dynamic polarizability varies linearly with the size (n) of the NO3-.nH2O cluster. It is found that the dynamic polarizability becomes infinite at a frequency of 6.12 eV. Display Omitted Highlights: → Preferential solvation instead of uniform solvation is observed for NO3-.nH2O (n>2) clusters. → Calculated polarizability varies linearly with the size of the cluster. → The dynamic polarizibilty become infinite at a frequency 6.12 eV. → A few water molecules are sufficient to mimic the bulk aqueous nitrate system. - Abstract: We report theoretical results on the structure, static, and dynamic polarizability of hydrated nitrate anion in finite size cluster, NO3-.nH2O (n = 1-8) based on the first principles electronic structure methods. The interesting observation is that for 3 ≤ n ≤ 8, the surface structures are more stable than the corresponding interior structures. It is observed that the polarizability (both static and dynamic) varies linearly with the size (n) of the hydrated cluster. It is found that the dynamic polarizability becomes infinite at a frequency of 6.12 eV. This observation is in very good agreement with the previously measured electronic transition energy corresponding to 6.13 eV for nitrate anion in aqueous solution.