X-ray diffraction and Raman spectroscopy investigations in concentrated aqueous solutions of yttrium and strontium nitrates

Ab initio and DFT study of Y3+ hydration

“…The formation enthalpy of the yttrium 3+ ion in aqueous solutions at infinite dilution is Δ f H(Y 3+ , aq) = −733.51 ± 2.07 kJ mol −1 43. The existence of the octaaquayttrium 3+ ions in aqueous solutions has been experimentally verified through XRD, XAFS, and Raman spectroscopy 5, 6. The existence of the nonaaquayttrium 3+ ions in crystalline nonahydrated trifluoromethanesulfonates has been experimentally verified by XRD and XAFS study 5, 44, 45.…”

“…Poor agreement was found between the calculated YO bond lengths at RHF and MP2 levels for the Y(H 2 O) aqua ion and those obtained experimentally by the different extended X‐ray measurements 1–6 (Table I). The present study has shown that the inclusion of the secondary hydration sphere gives shortening YO bonds by only 0.015–0.02 Å.…”

“…However, experimental data for the coordination number of the Y 3+ cation in aqueous solution are very contradictory. For instance, values ranging from 8 to 10 were found in different XRD and Raman experiments for the Y 3+ aqua cation 1–6.…”

“…The AXS studies indicate that 8–9 water molecules are coordinated 1. Raman spectroscopy suggests that the yttrium 3+ hydration number is 8 6.…”

“…Trivalent Y 3+ ions are strongly hydrated in aqueous solutions because of the high charge‐to‐ionic radius ratio. Hydration numbers for the Y 3+ ion have been investigated using a number of methods, which include anomalous X‐ray scattering (AXS) 1, extended X‐ray adsorption fine structure (EXAFS) 2–4, X‐ray diffraction (XRD) 5, 6, X‐ray absorption fine structure (XAFS) 5, and Raman spectroscopy (RS) 2,6. Previously published structural characteristics of the yttrium 3+ aqua ion are given in Table I for inter‐comparison.…”