Local order in concentrated aqueous solutions of yttrium chloride and bromide

Abstract

X-ray diffraction patterns of equimolecular concentrated aqueous solutions of yttrium chloride and bromide have been investigated from s=0.4 AA-1 up to s=15 AA-1. An assumed coordination of eight water molecules around each yttrium cation, at a distance of 2.36 AA, reproduces the intensity at high s values in agreement with the values obtained by some of the present authors from EXAFS experiments. Narrow interference maxima at s=(4 pi sin theta )/ lambda approximately=0.9 AA-1 may be interpreted as the existence of a local order of the hydrated yttrium cations surrounded by anions and free water molecules. Structural models with and without close packing of the hydrated cations were built to simulate that local order.