Solution Structure of NaNO₃ in Water: Diffraction and Molecular Dynamics Simulation Study

Abstract

The structure of a series of aqueous sodium nitrate solutions (1.9-7.6 M) was studied using a combination of experimental and theoretical methods. The results obtained from diffraction (X-ray, neutron) and molecular dynamics simulation have been compared and the capabilities and limitations of the methods in describing solution structure are discussed. For the solutions studied, diffraction methods were found to perform very well in description of hydration spheres of the sodium ion but do not yield detailed structural information on the anion's hydration structure. Molecular dynamics simulations proved to be a suitable tool in the detailed interpretation of the hydration sphere of ions, ion pair formation, and bulk structure of solutions.

On the influence of molecular structure on the conductivity of electrolyte solutions - sodium nitrate in water

“…Pair correlation functions, energies and other structural quantities were calculated for the model systems, and we found a satisfactory agreement with the structural information derived from x-ray and from neutron diffraction measurements for the real solutions [22]. In addition to the correlation functions 43006-2 presented in [22] here we show our results for the ion-ion correlations from MD and MC simulations for six solutions of different concentrations. In the case of molecular ions, we consider every atom of the NO ¿ -ion to be one site with a partial charge.…”

“…For the nitrate ion we used the values given in [22]. In addition to the MD simulations for the four solutions studied in [22] we have also performed MD and MC simulations of aqueous sodium nitrate solutions with concentrations of ¼º mol dm ¿ [24] and of º mol dm ¿ [25]. Pair correlation functions, energies and other structural quantities were calculated for the model systems, and we found a satisfactory agreement with the structural information derived from x-ray and from neutron diffraction measurements for the real solutions [22].…”

“…In addition to the MD simulations for the four solutions studied in [22] we have also performed MD and MC simulations of aqueous sodium nitrate solutions with concentrations of ¼º mol dm ¿ [24] and of º mol dm ¿ [25]. Pair correlation functions, energies and other structural quantities were calculated for the model systems, and we found a satisfactory agreement with the structural information derived from x-ray and from neutron diffraction measurements for the real solutions [22]. In addition to the correlation functions 43006-2 presented in [22] here we show our results for the ion-ion correlations from MD and MC simulations for six solutions of different concentrations.…”

Toward the understanding of hydration phenomena in aqueous electrolytes from the interplay of theory, molecular simulation, and experiment

“…has been characterized as exhibiting mild interactions with water, i.e., weakly hydrated as a result of its small charge and relatively large effective ionic that induce limited distortion of the hydrogen bonding of the surrounding water [172][173] . These features might have contributed to the large disparity in the reported water coordination of the nitrate anion from different experimental sources, including NMR [174][175][176][177][178][179][180] , IR [181][182][183][184][185][186][187] , Raman [173][174][188][189][190][191][192][193][194][195][196][197] , XRD 172-173, 190, 193, 195-204 , as well as NDIS [205][206][207][208][209][210] , and point to unresolved concerns regarding the determination and interpretation of the hydration microstructure of nitrates in a variety of aqueous environments 63 .…”

Hydration and Ion-Pair Formation of NaNO3(aq): A Vibrational Spectroscopic and Density Functional Theory Study

“…Structural methods such as neutron diffraction (ND) and X-ray diffraction have contributed to the characterization of hydration and ion pairing effects in NaNO 3 and other alkaline nitrates solutions. 4–8 A more recent neutron diffraction with isotopic substitution measurement and molecular dynamics (MD) simulation were both applied to study CsNO 3 and Cs 2 CO 3 in solution and showed that both hydration and ion pairing are weak for nitrate compared with carbonate. Simulations of nitrate water interactions on microhydrated NO3 - were carried out on discreet NO3 - H 2 O clusters with one to eight water molecules and theoretical IR spectra were given.…”