Abstract

Grandreefite, Pb2F2SO4, has been determined to be monoclinic rather than orthorhombic as reported in its origrnal description. Its cell parameters are a = 8.667(1), b = 4.4419(6), c = 14.242(2) Å, β = 107.418(2)°(Z = 4) and the space group is A2/a. The crystal strucrure, refined to R = 0.032 for 399 observed reflections, consists of layer fragments of the β-PbF2 structure parallel to (100) alternating with layers of isolated sulfate tetrahedra. The layer sequence in the unit cell is SO4-PbF2Pb-SO4-PbF2Pb-SO4. Pb is coordinated to four F and four O forming a distorted bicapped trigonal prism. The structure of grandreefite is closely related to that of the lanthanide oxide sulfates, Ln2O2SO4. Electrostatic bond strength and empirical bond-valence considerations suggest that the topologies of the structures differ with respect to the ligation of the sulfate oxygen atoms to the large cations.

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.