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

Some ion-associated species existed possibly in NaNO3solution were investigated via the ab-initio method. The hydrated ion parings,triple and multiple ion clusters in NaNO3solution are all analogous to those in Mg(NO3)2system except that the bi-dentate structures can not be formed.Only one solvent-shared ion paring has larger v1-NO3~- frequency than the hydrated NO3~- ion.And all triple clusters with two hydrated Na~+ ions and one NO3~- have larger v1-NO3~- frequency than the hydrated NO3~- ion.The ion association process in NaNO3solution 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 MgSO4but those in Mg(NO3)2and Mg(ClO4)2systems.