Three new alluaudite-like protonated arsenates: NaMg3(AsO4)(AsO3OH)2, NaZn3(AsO4)(AsO3OH)2 and Na(Na0.6Zn0.4)Zn2(H0.6AsO4)(AsO3OH)2

Tamara Ðorđević; Astrid Wittwer; Sergey V. Krivovichev

doi:10.1127/ejm/2015/0027-2458

Titel

Autor*in

Tamara Ðorđević

Institut für Mineralogie und Kristallographie, Fakultät für Geowissenschaften, Geographie und Astronomie, Universität Wien

Astrid Wittwer

Institut für Mineralogie und Kristallographie, Fakultät für Geowissenschaften, Geographie und Astronomie, Universität Wien

Sergey V. Krivovichev

St. Petersburg State University

Abstract

Three new arsenates NaMg3(AsO4)(AsO3OH)2 (1), NaZn3(AsO4)(AsO3OH)2 (2) and Na(Na0.6Zn0.4)Zn2(H0.6AsO4)(AsO3OH)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-group compounds. 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) Å, β = 112.67(3)/112.79(3)/113.83(3)°, V = 921.3(4)/926.7(4)/973.0(4) Å3, Z = 4, for 1, 2, and 3 respectively]. The crystal structures consist of chains of edge-sharing M1O4(OH)2 and M2O6, octahedra (M1, M2 = Mg for 1, M1, M2 = Zn for 2, and M1= Na, Zn, M2 = Zn for 3) that are stacked parallel to (101) and are connected by the AsO4 tetrahedra. These chains produce two types of channels parallel to the c-axis. Na atoms are located in the second-type channels, while hydrogen atoms of the OH groups are situated in the channels of the first-type. To obtain further information on the anion groups and especially on the short hydrogen bonds, infrared and single-crystal Raman spectra were measured and evaluated. The OH stretching frequency is in good agreement with the observed O···O distances. Furthermore, crystal chemistry of synthetic alluaudite-like arsenates is discussed.

Stichwort

arsenatesalluauditescrystal structuresingle-crystal X-ray diffractionhydrothermal synthesisInfrared spectroscopyRaman spectroscopy

Objekt-Typ

preprint

Sprache

Englisch [eng]

Persistent identifier

phaidra.univie.ac.at/o:474335

DOI

10.1127/ejm/2015/0027-2458

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