ATHENEITE, [Pd-2][As0.75Hg0.25], FROM ITABIRA, MINAS GERAIS, BRAZIL: CRYSTAL STRUCTURE AND REVISION OF THE CHEMICAL FORMULA

作者：Bindi Luca^*

来源：The Canadian Mineralogist, 2010, 48(5): 1149-1155.

DOI：10.3749/canmin.48.5.1149

• atheneite
• Pd arsenides
• structure solution
• crystal-structure refinement
• chemical analysis

The crystal structure of the rare mineral atheneite was solved using intensity data collected from a crystal from Itabira, Minas Gerais, Brazil. The structure is hexagonal, space group P (6) over bar 2m, with a = 6.813(1), c = 3.4892(5) angstrom and V = 140.26(4) angstrom(3). The refinement of an anisotropic model led to an R index of 7.26% for 261 independent reflections. The crystal structure strongly resembles that of synthetic MM'As compounds, with M = Ru, Rh, Pd, and M = 3d transition element. There are two fully occupied Pd sites: site Pd1 has a ten-fold coordination, and Pd2, an eleven-fold coordination. The two As atoms in the structure have a tricapped trigonal prismatic coordination; As1 is filled by arsenic only, whereas As2 has an occupancy of 0.60 As and 0.40 Hg. The presence of Hg at the As2 site accounts for the longer distances observed. On the basis of information gained from this characterization, the crystal-chemical formula was revised according to the structural results, yielding Pd-2[As0.75Hg0.25] (Z = 3) instead of (Pd,Hg)(3)As (Z = 2) as previously reported. A recalculation of the chemical data listed in the scientific literature for atheneite according to the structural results obtained here leads to an excellent agreement.

• 出版日期2010-10