The structure of antimonian dussertite, Ba(Fe (super 3+) (sub 0.84) , Sb (super 5+) (sub 0.16) ) 3 (AsO 4 ) 2 (OH,H 2 O) 6 , has been refined in space group R3m with a 7.410(3), c 17.484(4) Aa, Z = 3, to R = 3.2% and R w = 3.7% using 377 observed reflections with I> or =3 sigma (I). The structure is of the alunite-type and consists of sheets of corner-sharing (Fe (super 3+) , Sb (super 5+) )O 6 octahedra parallel to (0001). The substitution of Sb (super 5+) for Fe (super 3+) , and not for As (super 5+) , is unambiguously demonstrated not only by the structure refinement but also by electron microprobe analyses and crystal-chemical considerations. The icosahedrally coordinated Ba cations occupy cavities between pairs of octahedral sheets and are surrounded by six O atoms from the AsO 4 tetrahedra and six O atoms from the (Fe (super 3+) ,Sb (super 5+) )O 6 octahedra. The mean bond lengths for the various coordination polyhedra are As-O 1.684(3) Aa, (Fe,Sb)-O 2.004(1) Aa, and Ba-O 2.872(2) Aa. A hydrogen-bonding network is modelled using bond-valence calculations. The dussertite sample investigated is the first member of the crandallite group found to contain substantial Sb.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.