Reexamination of the crystal structure of semseyite

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Marco E. Ciriotti
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Reexamination of the crystal structure of semseyite

Messaggio da Marco E. Ciriotti » mar 19 dic, 2017 11:03

Prossima pubblicazione.

▪ Matsushita, Y. (2018): Reexamination of the crystal structure of semseyite, Pb9Sb8S21. Zeitschrift für Kristallographie - Crystalline Materials, 233, (in press).

The crystal structure of semseyite, Pb9Sb8S21 was successfully refined using a single-crystal specimen from Wolfsberg, Harz, Germany, having chemical composition (EPMA) Pb9.01(1)Sb8.00(3)S21.05(5). The structure belongs to the monoclinic C2/c space group (a=13.6267(10) Å, b=11.9742(9) Å, c=24.5891(18) Å, β=105.997(3)°, V=3856.8(5) Å3, Z=4, Dc=6.048 g/cm3). Crystal structure refinement with all atoms refined anisotropically converged to R1=4.64% (I>2σ(I)). The crystal structure is built of two subunits (A and B) showing TlSbS2-like topology. Each of them stacks parallel to (001), and c/2 in thickness. Two cation sites (Pb1 and Sb5) located at central part of the subunit, show mixed occupancy behavior as 95% Pb and 5% Sb at the Pb5 site, and 95% Sb and 5% Pb at the Sb1 site, respectively. Each of subunits are related by unit cell-level twinning mechanism “tropochemical cell twinning” with the TlSbS2-like subunits alternatively parallel to (1 1 −4) and (−1 1 4) planes.
Marco E. Ciriotti

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