Large ionic clusters in concentrated aqueous NaCl solution

Abstract

The stability of the local structure of aqueous 1.0 M NaCl solution at 293 K was investigated by molecular dynamics simulations. The mean and maximum life-times of the ion pairs were determined to be 0.13, 0.14 and 0.27 ps for negatively charged, neutral and positively charged ions pairs, respectively. The stability of non-neutral ion pairs was studied from the structure of the anion–cation radial distribution function and other structural functions. We found that non-neutral ions pairs are stabilized by at least one counter-ion forming in this way large ionic clusters that include the hydration molecules. About 25% of the ions are included in neutral clusters formed by a minimum of four ions. The existence of these large clusters obfuscates the commonly accepted chemical reaction scheme for the interconvention of ion pairs in aqueous solutions.