The crystal structure of alamosite, PbSiO31

Abstract
Alamosite, PbSiO 3 , has space group P 2/ n with cell parameters for the reduced cell a = 11.23 Å, b = 7.08 Å, c = 12.26 Å, and β = 113° 15′, with Z = 12. The structure has been determined using three-dimensional counterdiffractometer data. Refinement converged with R = 11.1%, including a number of reflections omitted due to extinction effects. The structure of alamosite is unique in that it consists partially of chains of tetrahedra extending parallel to [10[unk]] with a lattice translation repeat of twelve tetrahedra. The three independent Pb atoms are coordinated by 3 or 4 oxygen atoms, in each case the nearest oxygen neighbors being distributed on one side of the Pb atom, indicating covalency in Pb–O bonding. The Pb atoms and their coordinating oxygen atoms are related by an approximation to a 3 1 screw axis parallel to [010] so that they form a continuous spiral of bonded Pb, O atoms.

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