Crystal structure of mahnertite

Authors: Pushcharovsky, Dmitry . Y.u.; Zubkova, Natalia V.; Teat, Simon J.; Maclean, Elizabeth; Sarp, Halil

Source: European Journal of Mineralogy, Volume 16, Number 4, 1 August 2004 , pp. 687-692(6)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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Abstract:

Mahnertite, (Na_0.88 Ca_0.12)Cu_2.75 [AsO₄]₂Cl_0.62 ·3.63 H₂O, M = 565.17, is tetragonal, with space group I4/ mmm,a = 10.037(1),c = 23.739(1) Å,V = 2391.5(4) Å 3 ,Z = 8, o = 3.32, rho

c = 3.14 g/cm³,

= 9.78 mm^-1. The crystal structure of mahnertite was solved and refined against data collected at the Daresbury S ynchrotron Radiation Source, using a 20 × 20 × 2

m³ single crystal, lambda

= 0.6898 Å, F (000) = 2150, R = 0.049 for 639 reflections with I > 2 sigma

(I). The structure consists of sheets parallel to (001), which comprise two symmetrically independent distorted Cu 5-vertex square pyramids Cu phgr

5 (

= O, Cl or H₂ O) as well as AsO₄ tetrahedra. Four Cu phgr

5 pyramids located around the 4-fold axis share e dges to form clusters linked by AsO⁴ tetrahedra. The sheets are linked by the common apical vertex of the Cu(2) phgr

< 5 polyhedra. As a result, a heterogeneous framework is formed. (Na, Ca) atoms, additional Cu(3) cations and H² O molecules are located in the interlayers. The mineral is structurally related to zdenekite, NaPbCu<₅ (AsO₄)₄ Cl sdot