Neutron and X-ray diffraction measurements on highly concentrated aqueous LiCl solutions

Abstract

New neutron and X-ray diffraction experiments have been performed on concentrated aqueous lithium chloride (LiCl) solutions under ambient conditions, as a function of the salt concentration. The concentration range covers a wide region, between ion-pair:water ratios of about 1:3 (which is about the solubility limit) and 1:15 (which is still rather high a concentration value). Data have been interpreted by means of the Reverse Monte Carlo structural modelling method. It has been established that meaningful ion–water and water–water partial radial distribution functions may be derived even from such limited amount of diffraction data, provided that the diffraction measurements and the method of interpreting them are chosen sensibly. The new data and their analyses suggest the presence of Li + cations with only 3 (or less) coordinated water molecules around them. At the highest concentration, one counter-ion has been found to penetrate into the first hydration sphere of the ions.