TY - JOUR
T1 - Structure, phase transitions and ionic conductivity of K3NdSi6O15·xH2O. II. Structure of β-K3NdSi6O15
AU - Haile, S. M.
AU - Wuensch, B. J.
PY - 2000/6
Y1 - 2000/6
N2 - Hydrothermally grown crystals of β-K3NdSi6O15, potassium neodymium silicate, have been studied by single-crystal X-ray methods. Under appropriate conditions, the compound crystallizes in space group Bb21m and has lattice constants a = 14.370 (2), b = 15.518 (2) and c = 14.265 (2) Å. There are 30 atom sites in the asymmetric unit of the basic structure. With eight formula units per unit cell, the calculated density is 2.798 Mg m-3. Refinement was carried out to a residual, wR(F2), of 0.1177 [R(F) = 0.0416] using anisotropic temperature factors for all atoms. The structure is based on (Si2O52-)∞ layers, connected by Nd polyhedra to form a three-dimensional framework. Potassium ion sites, some of which are only partially occupied, are located within channels that run between the silicate layers. The silica-neodymia framework of β-K3NdSi6O15, in particular the linkages formed between the silicate layers and Nd polyhedra, bears some similarities to that of the essentially isocompositional phase α-K3NdSi6O15·2H2O. In both, the silicate layers are corrugated so as to accommodate a simple cubic array of NdO6 octahedra with lattice constant ∼ 7.5 Å. Furthermore, the Si2O5 layers in β-K3NdSi6O15 are topologically identical to those of the mineral sazhinite, Na2HCeSi6O15. Although β-K3NdSi6O15 and sazhinite are not isostructural, the structures of each can be described as slight distortions of a high-symmetry parent structure with space group Pbmm.
AB - Hydrothermally grown crystals of β-K3NdSi6O15, potassium neodymium silicate, have been studied by single-crystal X-ray methods. Under appropriate conditions, the compound crystallizes in space group Bb21m and has lattice constants a = 14.370 (2), b = 15.518 (2) and c = 14.265 (2) Å. There are 30 atom sites in the asymmetric unit of the basic structure. With eight formula units per unit cell, the calculated density is 2.798 Mg m-3. Refinement was carried out to a residual, wR(F2), of 0.1177 [R(F) = 0.0416] using anisotropic temperature factors for all atoms. The structure is based on (Si2O52-)∞ layers, connected by Nd polyhedra to form a three-dimensional framework. Potassium ion sites, some of which are only partially occupied, are located within channels that run between the silicate layers. The silica-neodymia framework of β-K3NdSi6O15, in particular the linkages formed between the silicate layers and Nd polyhedra, bears some similarities to that of the essentially isocompositional phase α-K3NdSi6O15·2H2O. In both, the silicate layers are corrugated so as to accommodate a simple cubic array of NdO6 octahedra with lattice constant ∼ 7.5 Å. Furthermore, the Si2O5 layers in β-K3NdSi6O15 are topologically identical to those of the mineral sazhinite, Na2HCeSi6O15. Although β-K3NdSi6O15 and sazhinite are not isostructural, the structures of each can be described as slight distortions of a high-symmetry parent structure with space group Pbmm.
UR - http://www.scopus.com/inward/record.url?scp=0003880078&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0003880078&partnerID=8YFLogxK
U2 - 10.1107/S0108768199015797
DO - 10.1107/S0108768199015797
M3 - Article
AN - SCOPUS:0003880078
SN - 0108-7681
VL - 56
SP - 349
EP - 362
JO - Acta Crystallographica Section B: Structural Science
JF - Acta Crystallographica Section B: Structural Science
IS - 3
ER -