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- Title
Ordering of calcium and vacancies in calcium catapleiite CaZr[SiO] • 2HO.
- Authors
Aksenov, S.; Portnov, A.; Chukanov, N.; Rastsvetaeva, R.; Nelyubina, Yu.; Kononkova, N.; Akimenko, M.
- Abstract
A sample of holotypic calcium catapleiite from the Burpala alkaline massif (Northern Baikal, Russia) is studied by single crystal X-ray analysis at 120 K and IR spectroscopy. The empirical formula of calcium catapleiite is CaNaZrSiO • 2HO ( Z = 4). The X-ray diffraction study confirms the orthorhombic unit cell with the following parameters: a = 7.406(1), b = 12.687(1), and c = 10.112(1) Å; V = 950.1(2) Å; space group Pbnn. The crystal structure is refined in the anisotropic approximation of atomic displacement parameters using 1177 reflections with I > 2σ( I) to the final R = 2.91%. The structure of calcium catapleiite under study is based on the microporous heteropolyhedral framework formed by ZrO octahedra and threemembered silicon-oxygen rings [SiO]. It is on the whole analogous to the structures of the samples studied earlier, but differs from them by a high degree of ordering of calcium and vacancies at extraframework positions. The distribution of calcium over Ca1 and Ca2 positions in the calcium catapleiite structure leads to the formation of zigzag chains of the ...Сa1-Zr-Ca1-Zr... and ...Сa2-h-Ca2-□... types. Low occupancy of the Ca2 position and its alternation with the vacancy are prerequisites for potential Ca cationic conduction.
- Subjects
CALCIUM compounds; SINGLE crystals; X-ray diffraction; CRYSTAL structure; ANISOTROPY
- Publication
Crystallography Reports, 2016, Vol 61, Issue 3, p376
- ISSN
1063-7745
- Publication type
Article
- DOI
10.1134/S1063774516030020