The Crystal Structure and Crystal Chemistry of Mineral-like Cd₅(VO₄)₂(OH)₄, a Novel Isomorph of Arsenoclasite and Gatehouseite

Author(s)

Ljiljana Karanović, Tamara Đorđević

Abstract

The pentacadmium bis(vanadate(V)) tetrahydroxide Cd₅(VO₄)₂(OH)₄ was synthesized under hydrothermal conditions, and its crystal structure was determined with single-crystal X-ray diffraction. The investigated compound is the second known compound next to Cd(VO₃)₂·4H₂O synthesized in the CdO–V₂O₅–H₂O system and crystallizes isotypically to the minerals gatehouseite, Mn₅(PO₄)₂(OH)₄, and its As analog arsenoclasite, Mn₅(AsO₄)₂(OH)₄. Its symmetry is orthorhombic, with a space group of P2₁2₁2₁ and unit cell parameters of a = 19.011(4), b = 6.0133(12), c = 9.5411(19) Å, V = 1090.7(4) Å3, and Z = 4. The structure consists of double ribbons of M(O,OH)₆-octahedra (M = Cd2, Cd3, Cd4) extending along [010] interconnected by edge- and corner-shared M(O,OH)₆-octahedra (M = Cd1, Cd5) and discrete, slightly distorted VO₄ tetrahedra, which form double chains of coupled polyhedra [V1O₄–Cd₅O₄(OH)₂–Cd1O₅(OH)–V₂O₄]_n running along the same direction. The interesting feature is the existence of V–Cd distances (3.0934(7) and 3.1081(7) Å for V1–Cd5 and V2–Cd1, respectively), which are shorter than the sum of the van der Waals radii of 3.71 Å. The V1–V2 distances of 4.1214(9) Å are also shorter than the sum of the van der Waals radii of 4.26 Å. The O–H···O hydrogen bonds additionally link the two subunits, ribbons, and chains into a three-dimensional structure. Raman spectra confirmed the presence of the hydrogen bonds and mutually isolated VO₄ groups.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

University of Belgrade

Journal

Minerals

Volume

12

No. of pages

13

ISSN

2075-163X

DOI

https://doi.org/10.3390/min12121601

Publication date

12-2022

Peer reviewed

Yes

Austrian Fields of Science 2012

105116 Mineralogy, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Geology, Geotechnical Engineering and Engineering Geology

Portal url

https://ucrisportal.univie.ac.at/en/publications/c83db787-0e9e-4758-ae71-9393cd6d2dbd