BaMgAs2O7 and BaCoAs2O7 - Synthesis, crystal structures and twinning of two new barium diarsenates
- Author(s)
- T Mihajlovic, Uwe Kolitsch, Herta Silvia Effenberger
- Abstract
The monoclinic crystal structures of two hydrothermally synthesized Ba-M2+-diarsenates (M=Mg, Co) were determined from single-crystal X-ray diffraction data (Mo Ka, 298K) obtained from crystals twinned by non-merohedry; the twin plane is (100). BaMgAs2O7/ BaCoAs2O7 have a=5.620(1)/5.649(1), b=8.629(2)/8.577(1), c.344(3)/13.278(2)A°, ß�.20(3)/90.014(1)°, Vd7.1(2)/643.3(2)A°3, space group P21/n, Z=4. The crystal structures were refined to R1(F)=0.024/0.022 and wR2(F 2)=0.052/0.048 for the 2349/2347 unique reflections with 2?e° and 102 free parameters (for the 2269/2286 'observed reflections' with Fo2=4s(Fo2) R1(F) is 0.023/0.021). Both diarsenates are isotypic with a series of compounds with the general formula M(1)2+M(2)2+X 2O7 (M(1) = Ca, Sr, Ba, Pb; M(2) = Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd; X=P, As). The framework structure is characterized by corner-sharing M(2)O5 square pyramids and X2O7 groups where the M(1) atoms occupy channels. The non-merohedric twinning, related to the strongly pseudo-orthorhombic cell metrics, is discussed. Œ 2004 Elsevier B.V. All rights reserved.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- University of Vienna
- Journal
- Journal of Alloys and Compounds
- Volume
- 379
- Pages
- 103-109
- No. of pages
- 7
- ISSN
- 0925-8388
- DOI
- https://doi.org/10.1016/j.jallcom.2004.02.016
- Publication date
- 2004
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/cd86f9cf-6fa8-4a28-aad1-afae38841d76