Acentric structure (P3) of bechererite, Zn₇Cu(OH)₁₃[SiO(OH)₃SO₄]

Autor(en)

universität bern, Thomas Armbruster, Gerald Giester

Abstrakt

The crystal structure of bechererite from the Tonopah-Belmont mine, Arizona, was reinvestigated using a single-crystal x-ray diffraction (MoKalpha radiation) equipped with a charge-coupled device area detector. The structure was refined in space group P3 (a = 8.319(2), c = 7.377(1) .ANG.) with 1247 unique reflections up to (sinq)/lambda = 0.65 leading to R1 = 2.7%, wR2 = 6.4%. In agreement with the previously reported centric structure (P.hivin.3), bechererite is composed of (001) brucite-like sheets formed by edge-sharing (Zn,Cu)O6 octahedra and 1/7 ordered octahedral vacancies. The layers are connected parallel to c by ditetrahedral (Zn,Cu)2(OH)7 units. Due to the attractive force of a weak hydrogen bond, the bridging O atom of the ditetrahedral unit is displaced from the threefold axis. A characteristic feature of the structure is isolated tetrahedra, which connect only with one apex to the octahedral sheet. The acentric structure (P3) reveals ordering between SiO(OH)3 and SO4 tetrahedra yielding characteristics distortions of the neighboring (Zn,Cu)O6 octahedra caused by bond-valence requirements of the shared O atoms. The [SiO(OH)3]1- tetrahedron is only 70(1)% occupied and is partly substituted by tetrahedral [O4H7]1- clusters. The existence of H2O mols. in the [O4H7]1- cluster is supported by FTIR spectroscopy.

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Universität Bern

Journal

The American mineralogist

Seiten

1014-1018

Anzahl der Seiten

5

ISSN

0003-004X

DOI

https://doi.org/10.2138/am-1997-9-1018

Publikationsdatum

09-1997

Peer-reviewed

Ja

ÖFOS 2012

105113 Kristallographie, 105116 Mineralogie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/acentric-structure-p3-of-bechererite-zn7cuoh13siooh3so4(135ec061-0a56-4e65-b4b8-2082d5d31313).html