Concentration-Dependent Structure Of Mixed Nh4cl And (Nh4)(2)So4 Aqueous Solutions From The X-Ray Diffraction, Raman Spectroscopy And Molecular Dynamics Simulations

Influences of concentration on micro structures of mixed NH4Cl and (NH4)(2)SO4 aqueous solutions are investigated by Raman spectroscopy, X-ray diffraction spectroscopy and molecular dynamics simulations. We deduce the reduced pair distribution function G(r) from X-ray diffraction diagrams, obtain the radial distribution function (RDF) from the molecular dynamics simulations and get the excess Raman spectroscopy from Raman spectroscopy. The results above illustrate that the formation of interaction between NH4 thorn and SO42- causes a characteristic peak in the X-ray diffraction spectroscopy, which can be used to prove the existence of both NH4+ and SO42- in solutions. Besides, as the mixed concentrations change, two structural turning points appear. One turning point is mixed concentrations of 23% NH4Cl and 10% (NH4)(2)SO4, while the other one is mixed concentrations of 11% NH4Cl and 30% (NH4)(2)SO4. At these points, the old network structure and original ion contact pairs are damaged, while the new ion pairs are generated, due to the addition of mixed NH4Cl and (NH4)(2)SO4 in aqueous solutions. Furthermore, these conclusions of experimental and simulated test are completely consistent and mutually supportive. (C) 2019 Published by Elsevier B.V.