Three new alluaudite-like protonated arsenates: NaMg₃(AsO₄)(AsO₃OH)₂, NaZn₃(AsO₄)(AsO₃OH)₂ and Na(Na_0.6Zn_0.4)Zn₂(H_0.6AsO₄)(AsO₃OH)₂

Author(s)

Tamara Đorđević, Astrid Wittwer, Sergey V. Krivovichev

Abstract

Three new arsenates, NaMg

₃(AsO

₄)(AsO

₃OH)

₂ (1), NaZn

₃(AsO

₄)(AsO

₃OH)

₂ (2) and Na(Na

_0.6Zn

_0.4)Zn

₂(H

_0.6AsO

₄) (AsO

₃OH)

₂ (3), were synthesised under low-temperature hydrothermal conditions. 1 is the first example of a synthetic hydrous Na-Mg arsenate, and 2 and 3 are the first synthetic hydrous Na-Zn arsenates with octahedrally coordinated Zn atoms. They are all isostructural with the protonated members of the alluaudite-supergroup compounds; 2 is synthetic end-member of o’danielite. Their crystal structures were determined from the single-crystal X-ray diffraction data collected at 293 K [space group C2/c, a = 11.972(2)/12.023(2)/12.458(3), b = 12.367(3)/12.385(3)/12.484(3), c = 6.743(2)/6.750(2)/6.839(2) A°, b = 112.67(3)/112.79(3)/113.83(3), V = 921.3(4)/926.7(4)/973.0(4)A° 3, Z = 4, for 1, 2, and 3 respectively]. The crystal structures consist of chains of edge-sharing M1O

₄(OH)

₂ and M

₂O

₆ octahedra (M1,M2=Mg for 1,M1,M2=Zn for 2, andM1= Na, Zn,M2=Zn for 3) stacked parallel to (101) and connected by the AsO

₄ tetrahedra. These chains form two types of channels parallel to the c-axis. While hydrogen atoms of the OH groups are situated in the channels of the first type, Na atoms are located in the second-type channels. Infrared and single-crystal Raman spectra were measured and evaluated in order to obtain further information on the anion groups and especially on the short hydrogen bonds. The OH stretching frequency is in good agreement with the observed O … O distances. Furthermore, the crystal chemistry of synthetic alluaudite-like arsenates is discussed in terms of structure distortion and measure of similarity among them.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Saint Petersburg State University

Journal

European Journal of Mineralogy: an international journal of mineralogy, geochemistry and related sciences

Volume

27

Pages

559-573

No. of pages

15

ISSN

0935-1221

DOI

https://doi.org/10.1127/ejm/2015/0027-2458

Publication date

04-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

104011 Materials chemistry, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Geochemistry and Petrology

Portal url

https://ucrisportal.univie.ac.at/en/publications/three-new-alluauditelike-protonated-arsenates-namg3aso4aso3oh2-nazn3aso4aso3oh2-and-nana06zn04zn2h06aso4aso3oh2(7f526396-a4fc-4628-b5b4-990c8e1b9104).html