Neutron Diffraction Study of Aqueous Ionic Solutions. II. Aqueous Solutions of Sodium Chloride and Potassium Chloride

Abstract The structure factors Sm(Q) for aqueous solutions of NaCl and KCl at room temperature have been determined by means of the LINAC-TOF-neutron diffraction method. A revised subtraction method was applied to diffraction data of the solutions. Results obtained for the structure of the nearest hydration shell around ions are as follows, (a) The coordination numbers are 8 for Na+ and 6 for Cl− in the NaCl solution and 8 for K+ and 6 for Cl− in the KCl solution; (b) the average ion-oxygen distances are 2.50±0.10 Å for Na+, 2.70±0.10 Å for K+, and 3.10±0.05 Å for Cl−; (c) around chloride ions water molecules take the configuration to orient the vector which bisects the D–O–D angle on a straight line joining an oxygen atom and the anion. Analysis was performed on the data of LiCl and CsCl solutions.