2007/08/01 by Sergey V. Krivovichev, С. К. Филатов, Peter C. Burns +1 · 1 citation
Materials Science · Physics and Astronomy · #Crystal Structures and Properties #Advanced Condensed Matter Physics #Polyoxometalates: Synthesis and Applications
paper · doi:10.2113/gscanmin.45.4.929
openalex publication_date 2007/08/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/07
The crystal structure of parageorgbokiite, β-Cu 5 O 2 (SeO 3 ) 2 Cl 2 , a new mineral species from the fumaroles of the Great Fissure Tolbachik eruption, in the Kamchatka Peninsula, Russia, has been solved from single-crystal X-ray-diffraction data by direct methods and refined to R 1 = 0.032 for 1388 unique reflections with | F o | ≥ 4σ F . The mineral is monoclinic, space group P 2 1 / c , a 5.3982(5), b 8.0543(8), c 11.1277(10) A, β 99.258(2)°, V 477.52(8) A 3 , Z = 2. The structure contains three symmetrically unique Cu positions, each octahedrally coordinated by O 2− and Cl − anions. There is one symmetrically independent Se 4+ cation coordinated by three O atoms, to form SeO 3 trigonal pyramids. The structure of parageorgbokiite is best described in terms of arrangements of the strong M –O bonds ( M = Se 4+ and Cu 2+ ). The O1 atom is not bonded to Se 4+ cations and is tetrahedrally coordinated by four Cu 2+ cations, which results in the formation of an oxocentered O1Cu 4 tetrahedron. Two O1Cu 4 tetrahedra share a Cu3...Cu3 edge to form O 2 Cu 6 dimers that are further linked by sharing the Cu2 corners to form O 2 Cu 5 infinite chains parallel to the a axis. The SeO 3 pyramids are attached to the faces of the oxocentered tetrahedra in a “face-to-face” position to form complex ([O 2 Cu 5 ][SeO 3 ] 2 ) 2+ chains and a three-dimensional framework with channels occupied by the Cl − anions. A comparison of parageorgbokiite and georbokiite shows that the two minerals have the same space group P 2 1 / c (monoclinic), but differ in their unit-cell parameters. The structures of both minerals are based upon the same complex ([O 2 Cu 5 ][SeO 3 ] 2 ) 2+ chains. However, the arrangements of the chains in the structures are different. The channels in parageorgbokiite are larger than those in georgbokiite. From the lower density of parageorgbokiite in comparison to georbokiite, we suggest that parageorgbokiite is a high-temperature modification of Cu 5 O 2 (SeO 3 ) 2 Cl 2 that is either chemically or kinetically stabilized at ambient conditions.