The crystal structure of podlesnoite, BaCa 2 (CO 3 ) 2 F 2

• Published in: Zeitschrift für Kristallographie
• Main Authors: Zubkova, Natalia V., Pushcharovsky, Dmitry Yu., Pekov, Igor V., Rabadanov, Murtazali Kh.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Walter de Gruyter GmbH 2007
• Subjects: Inorganic Chemistry; Condensed Matter Physics; General Materials Science; Kola Peninsula; Khibiny; kola peninsula
• Online Access: http://dx.doi.org/10.1524/zkri.2007.222.9.474; https://www.degruyter.com/document/doi/10.1524/zkri.2007.222.9.474/xml; https://www.degruyter.com/document/doi/10.1524/zkri.2007.222.9.474/pdf

Podlesnoite, BaCa 2 (CO 3 ) 2 F 2 , a fluorocarbonate mineral recently discovered at the Kirovskii mine, Khibiny alkaline massif, Kola Peninsula, Russia, is orthorhombic, Cmcm , a = 12.501(8) Å, b = 5.846(3) Å, c = 9.443(5) Å, V = 690.1(7) Å 3 , Z = 4, D calc = 3.614 g/cm 3 . The crystal structure was solved from 561 unique reflections with I > 2σ( I ) by direct methods and refined to R ( F ) = 0.0278, Rw ( F 2 ) = 0.0577. Podlesnoite is a representative of a new structure type slightly related to aragonite. The most specific feature of the podlesnoite structure is a honeycomb-like framework built by the columns of edge-sharing CaO 6 F 2 polyhedra; they are stretched parallel to the c axis. Interatomic bond-distances within these polyhedra vary from 2.2912(16) to 2.4883(15) Å. The CO 3 groups are parallel to the ac plane, the C—O bond distances range from 1.276(2) to 1.296(4) Å. The bond distances within BaO 6 F 4 polyhedra are 2.771(2) to 2.915(2) Å.