TY - JOUR

T1 - Crystal structure of a Carbonate-Nosean Na8[AlSiO4]6CO3

AU - Gesing, Thorsten M.

AU - Buhl, Josef Christian

PY - 1998/1/26

Y1 - 1998/1/26

N2 - The crystal structure of a nosean-analogous, carbonate-enclathrated compound of ideal composition Na8[AlSiO4]6CO3 (cubic, ao = 900.1(1) pm) was determined from powder data using the Rietveld method. The sample was prepared by annealing a basic nitrite sodalite solid solution in a stream of carbon dioxide (4,6 1/h) at elevated temperatures (873 K and 1023 K). The total ordering of the framework atoms Si(OAl)4 was revealed by a MAS NMR investigation of 29Si. In contrast to the sodalite structure, the cage-filling clusters [Na4CO3]2+ and [Na4]4+ are fully ordered. Space group P23 is confirmed along with the ordering of framework atoms. In accordance with the difference in size between the ordered guest ions, two independent positions for the framework oxygen atoms were found, each associated with a larger or a smaller cage type. These special features of the framework can also be ascertained from the split of the vs-mode in the 730 cm-1 region of the symmetric vibrations of the framework constituents in the IR spectra. The carbonate anion, with the carbon atom located at the central position, exhibits 12-fold orientational disorder within the β-cage. The sodium cations are distributed over two positions. From their coordinates, it is possible to derive the location of the cations inside the anion-free cages very close to the six-membered rings of the aluminosilicate framework. The configuration of the ions inside both types of cages should not be considered as static but rather on the basis of highly dynamical behaviour which leads to an optimal charge distribution between anion-containing cages and anion-free cages.

AB - The crystal structure of a nosean-analogous, carbonate-enclathrated compound of ideal composition Na8[AlSiO4]6CO3 (cubic, ao = 900.1(1) pm) was determined from powder data using the Rietveld method. The sample was prepared by annealing a basic nitrite sodalite solid solution in a stream of carbon dioxide (4,6 1/h) at elevated temperatures (873 K and 1023 K). The total ordering of the framework atoms Si(OAl)4 was revealed by a MAS NMR investigation of 29Si. In contrast to the sodalite structure, the cage-filling clusters [Na4CO3]2+ and [Na4]4+ are fully ordered. Space group P23 is confirmed along with the ordering of framework atoms. In accordance with the difference in size between the ordered guest ions, two independent positions for the framework oxygen atoms were found, each associated with a larger or a smaller cage type. These special features of the framework can also be ascertained from the split of the vs-mode in the 730 cm-1 region of the symmetric vibrations of the framework constituents in the IR spectra. The carbonate anion, with the carbon atom located at the central position, exhibits 12-fold orientational disorder within the β-cage. The sodium cations are distributed over two positions. From their coordinates, it is possible to derive the location of the cations inside the anion-free cages very close to the six-membered rings of the aluminosilicate framework. The configuration of the ions inside both types of cages should not be considered as static but rather on the basis of highly dynamical behaviour which leads to an optimal charge distribution between anion-containing cages and anion-free cages.

KW - Clathrated structure

KW - Crystal structure

KW - Na[AlSiO]CO

KW - Nosean

KW - Rietveld method

KW - X-ray powder diffraction

UR - http://www.scopus.com/inward/record.url?scp=0031941260&partnerID=8YFLogxK

U2 - 10.1127/ejm/10/1/0071

DO - 10.1127/ejm/10/1/0071

M3 - Article

AN - SCOPUS:0031941260

VL - 10

SP - 71

EP - 77

JO - European journal of mineralogy

JF - European journal of mineralogy

SN - 0935-1221

IS - 1

ER -