Powder Rietveld refinement of armstrongite, CaZr[Si6O15]·3H2O

✍ Scribed by Pushcharovsky, D.Yu.; Kabalov, K.; Zubkova, N.V.; Schneider, J.; Sapozhnikov, A.N.

• Book ID: 111964849
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 2000
• Tongue: English
• Weight: 508 KB
• Volume: 215
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.2000.215.12.757

✦ Synopsis

Crystal data and results of structure refinement using powder X-ray diffraction and Rietveld analysis for armstrongite, CaZr[Si~6~O~15~]·3H~2~O, are reported. Experimental data were collected using MoK~α1~ radiation over the range 2° - 51.98° 2θ. Armstrongite is monoclinic (space group C2, Z = 4), with a = 14.018(1) Å, b = 14.133(1) Å, c = 7.840(1) Å, β = 109.40(1)°. The crystal structure, reported by Kashaev and Sapozhnikov (1978) has been refined by Rietveld analysis, resulting in Rwp = 2.75. The structure is based on a heterogeneous octahedra-tetrahedra framework (ZrSi~6~O~15~) built by corrugated silicate sheets connected by ZrO~6~ octahedra. The seven-fold Ca polyhedron contains 2 H~2~O molecules. Two new sites for H~2~O molecules on the 2-fold axis in the voids of the zeolite like framework allowed to achieve the complete correspondence between chemical and structural data.