Ab-initio Investigation on Ion-associated Species and Association Process in NaNO3 Solution

Some ion-associated species existed possibly in NaNO3 solution were investigated via the ab-initio method. The hydrated ion parings, triple and multiple ion clusters in NaNO3 solution are all analogous to those in Mg(NO3)(2) system except that the bi-dentate structures can not be formed. Only one solvent-shared ion Paring has larger nu(1)-NO3- frequency than the hydrated NO3- ion. And all triple clusters with two hydrated Na+ ions and one NO3- have larger nu(1)-NO3- frequency than the hydrated NO3- ion. The ion association process in NaNO3 Solution is predicted as free ions -> solvent-separated ion pairings -> solvent-shared ion pairings -> solvent-shared triple ion clusters -> contact triple ion clusters -> contact multiple ion clusters amorphous NaNO3, which is not analogous to that in MgSO4 but those in Mg(NO3)(2) and Mg(ClO4)(2) systems.