Premium
(3+1)‐Incommensurately modulated crystal structure of Cs 3 ScSi 6 O 15
Author(s) -
Hejny Clivia,
Kahlenberg Volker,
Schmidmair Daniela,
Dabić Predrag
Publication year - 2016
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520615022076
Subject(s) - octahedron , crystallography , tetrahedron , valence (chemistry) , crystal structure , bar (unit) , physics , chemistry , materials science , quantum mechanics , meteorology
Single‐crystal X‐ray diffraction of Cs 3 ScSi 6 O 15 shows the presence of main reflections and satellite reflections up to the fourth order along the c* direction. The (3+1)‐dimensional incommensurately modulated structure was solved in superspace group [ a = 13.861 (1), c = 6.992 (1) Å, V = 1163.4 (2) Å 3 ] with a modulation wavevector q = 0.14153 (2) c* . Refinement of three modulation waves for positional and anisotropic displacement parameter values for all atoms converged to R obs values for all, main and satellite reflections of first, second and third order of 0.0200, 0.0166, 0.0181, 0.0214 and 0.0303, respectively. Cs 3 ScSi 6 O 15 forms a mixed tetrahedral–octahedral framework with prominent six‐membered rings of [SiO 4 ]‐tetrahedra interconnected by [ScO 6 ]‐octahedra. Apart from Sc, all atoms are strongly affected by positional modulation with maximum atomic displacements of up to 0.93 Å causing rigid polyhedral arrangements to perform tilt and twist movements relative to each other, such as a rotation of the Sc‐octahedra around the ‐axis by over 38°. Cs has an irregular coordination environment; however, considering distances up to 3.5 Å, the bond‐valence sum changes by no more than 0.02 as a function of t and thus overall kept at a level of ca 1.075.