Local structure and dynamics in concentrated aqueous solutions and glasses of univalent ions

We have analyzed the VV- and VH-Raman band profiles of the N–O symmetric stretching fundamental of the nitrate anion of 1 mol/ℓ NaNO3 (or LiNO3) in Li+Cl−-enriched aqueous solutions for the liquid phase between 263 and 353 K and for the vitreous state at 77 K. From the observed isothermal correlation time of the orientational mobility of the C3 axis of NO−3 in Li+-rich solution and from the band asymmetry of the corresponding isotropic profile at increasing temperature, we propose an endothermic local-structure-reforming process that favors incorporation of a few Li+ ions into the solvation sphere of the anions. The vitreous state of 1 mol/ℓ LiNO3 or NaNO3 in the LiCl-rich systems, which shows considerable local order about the nitrate anion, is conceptualized as a percolation cluster of solvated cation–anion interaction that breaks up into cluster distributions for the liquid phase.