NO₃– Coordination in Aqueous Solutions by ¹⁵N/¹⁴N and ¹⁸O/^natO Isotopic Substitution: What Can We Learn from Molecular Simulation?

We explore the deconvolution of water–nitrate correlations by the first-order difference approach involving neutron diffraction of heavy- and null-aqueous solutions of KNO₃ under ¹⁴N/¹⁵N and ^natO_N/¹⁸O_N substitutions to achieve a full characterization of the first water coordination around the nitrate ion. For that purpose we performed isobaric–isothermal simulations of 3.5 m KNO₃ aqueous solutions at ambient conditions to generate the relevant radial distribution functions required in the analysis (a) to identify the individual partial contributions to the total neutron-weighted distribution function, (b) to isolate and assess the contribution of NO₃^–···K⁺ pair formation, (c) to test the accuracy of the neutron diffraction with isotope substitution based coordination calculations and X-ray diffraction based assumptions, and (d) to describe the water coordination around both the nitrogen and oxygen sites of the nitrate ion.