Erbium selenates

The only study of the complex formation between selenate and trivalent lanthanides found is an X-ray diffraction investigation of some lanthanide selenate solutions by Johansson, Niinisto, and Wakita [85JOH/NI1], The radial distribution function was interpreted to show that inner-sphere complexes were formed. For Er an average of 0.4 SeO per Er was estimated for a solution containing 0.78 M Er and 1.55 M SeOj. The conditional equilibrium constant for the inner-sphere complex formation  

This value will not be included in the data selection. 

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Fig. 25. RDFs for 1 M erbium(III) perchlorate and selenate solutions after elimination of nonmetal interactions. The monodentate bonding of SeO is shown by the Er-Se peak in the RDF for the selenate solution.

It shows essentially the same structure than the erbium phase but one unit cell edge is doubled and the symmetry changes from Cc to Cljc. Nevertheless, a slight disorder of the selenate ion is still observable. 

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