Simulation models of the nearest environment of ions in aqueous gadolinium chloride solutions

The structure of aqueous gadolinium chloride solutions is studied within a broad concentration range under the standard conditions. The simulation approach is used to analyze experimental X-ray diffraction data; the structural parameters of the nearest environment of ions were determined in the solutions under study. The gadolinium ion in saturated and concentrated solutions is found to form a rigid hydration sphere consisting of six water molecules; further dilution can result in additional incorporation of up to 2.64 solvent molecules in the long-range environment. Thus, the average coordination number of gadolinium in dilute solutions is 8.6. The cation also forms a second coordination sphere. Non-contact ion associates are typical for all the systems under study.