Water in the Alluaudite Type-Compounds
- Author(s)
- Tamara Đorđević, Ljiljana Karanović, Marko Jagodic, Zvonco Jaglicic
- Abstract
In this study, a new cobalt arsenate belonging to the alluaudite supergroup compounds with the general formula of Co-3(AsO4)(0.5+x)(HAsO4)(2-x)(H2AsO4)(0.5+x)[(H,)(0.5)(H2O,H3O)(0.5)](2)(x+) (denoted as CoAsAllu) was synthesized under hydrothermal conditions. Its crystal structure was determined by a room-temperature single-crystal X-ray diffraction analysis: space group C2/c, a = 11.6978(8), b = 12.5713(7), c = 6.7705(5) & ANGS;, beta = 113.255(5)& DEG;, V = 914.76(11) & ANGS;(3), Z = 2 for As6H8Co6O25. It represents a new member of alluaudite-like protonated arsenates and the first alluaudite-like phase showing both protonation of the tetrahedral site and presence of the H2O molecules in the channels. In the asymmetric unit of CoAsAllu, one of the two Co, one of the two As and one of the seven O atoms lie at 4e special positions (site symmetry 2). The crystal structure consists of the infinite edge-shared CoO6 octahedra chains, running parallel to the [101 over bar ] direction. The curved chains are interconnected by [(As1O(4))(0.5)(H(2)As1O(4))(0.5)](2-) and [HAs2O4](2-) tetrahedra forming a heteropolyhedral 3D open framework with two types of parallel channels. Both channels run along the c-axis and are located at the positions (1/2, 0, z) and (0, 0, z), respectively. The H2 and H4 hydrogen atoms of O2H2 and O4H4 hydroxyl groups are situated in channel 1, while the uncoordinated water molecule H(2)O7 at half-occupied 4e special positions and hydrogen atoms of O6H6 hydroxyl group were found in channel 2. The results of the magnetic investigations confirm the quasi one-dimensional structure of divalent cobalt ions. They are antiferromagnetically coupled with the intrachain interaction parameter of J & AP; -8 cm(-1) and interchain parameter of J' & AP; -2 cm(-1) that become effective below the Neel temperature of 3.4 K.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- University of Belgrade, University of Ljubljana
- Journal
- Minerals
- Volume
- 11
- No. of pages
- 14
- ISSN
- 2075-163X
- DOI
- https://doi.org/10.3390/min11121372
- Publication date
- 12-2021
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 104026 Spectroscopy, 105116 Mineralogy, 104011 Materials chemistry, 105113 Crystallography
- Keywords
- ASJC Scopus subject areas
- Geology, Geotechnical Engineering and Engineering Geology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/b6facfa3-53f7-4a63-bc6f-c3ff5d0aa47a