Local structure refinement of disordered material models: ion pairing and structure in YCl3 aqueous solutions.

Hydrogen/deuterium isotopic neutron diffraction techniques have been used to investigate the structure of a 1 m aqueous solution of YCl3 at room temperature. Empirical potential structure refinement (EPSR) has been used to build a three-dimensional model of the solution structure that is consistent with the bulk solvent correlations strongly probed by the neutron scattering technique. Optimization of the local structural environment of the Y3+ ion sites within the model has been performed through calculations of the yttrium K-edge, extended X-ray absorption fine structure (EXAFS) spectrum of the solution, and detailed information has been extracted on the structure of the ion hydration shell and the extent of inner-sphere ion pairing within the solution. The results demonstrate the significant potential of this hybrid data analysis approach to circumvent the limitations of the individual experimental methods, to refine atomic potential models, and to produce accurate, quantitative structural models of the local environment of dilute atomic species within tightly constrained bulk network structures.