• journal_title：The Canadian Mineralogist
• Contributor：Sergey V. Krivovichev ; Stanislav K. Filatov ; Pavel N. Cherepansky ; Thomas Armbruster ; Olga Yu. Pankratova
• Publisher：Mineralogical Association of Canada
• Date：2005-
• Format：text/html
• Language：en
• Identifier：10.2113/gscanmin.43.2.671
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：43
• issue：2
• firstpage：671
• section：Articles

Single crystals of γ-Cu₂V₂O₇ were obtained by the method of chemical transport reactions. The crystal structure [triclinic, P1̅, a 5.0873(10), b 5.8233(11), c 9.4020(18) Å, α 99.780(3), β 97.253(3), γ 97.202(3)□, V 269.20(9) ų, Z = 2] has been solved by direct methods and refined to R₁ = 0.021 (wR₂ = 0.049) using 949 unique observed reflections with |F_o| ⋄ 4σ_F. The atomic arrangement contains two symmetrically independent Cu²⁺ cations. The Cu(1) site is coordinated by six O atoms to form a distorted Cu(1)O₆ octahedron, whereas the Cu(2) site is coordinated by five O atoms arranged at the vertices of an elongate Cu(2)O₅ square pyramid. Two symmetrically independent V⁵⁺ cations are tetrahedrally coordinated by four O atoms each. The O(5) atom bridges the V(1)O₄ and V(2)O₄ tetrahedra. The Cu(1)O₆ octahedra and Cu(2)O₅ square pyramids form two types of chains running parallel to the a axis. The chains are linked by V₂O₇ groups into a complex heteropolyhedral framework. The structure of γ-Cu₂V₂O₇ is closely related to the structures of α-Cu₂V₂O₇ (blossite) and β-Cu₂V₂O₇ (ziesite). The three structures are based upon chains of edge-sharing Cu²⁺ polyhedra linked by V₂O₇ groups. Similarity of the structure of γ-Cu₂V₂O₇ to the structures of blossite and ziesite indicates possible formation of this phase under natural conditions, such as those that occur in “dry” high-temperature fumaroles of the Izalco (El Salvador) and Tolbachik (Kamchatka, Russia) volcanoes. The structure of γ-Cu₂V₂O₇ can also be considered as a triclinically distorted derivative of the β-A₂P₂O₇ structure-type.