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Self‐Intercalation and Vacancy‐Ordering in 6R‐Cu x Ta 1+ y S 2 ( x ≈ 0.23, y = 0, 0.06)
Author(s) -
Ali Sk Imran,
Mondal Swastik,
Prathapa Siriyara Jagannatha,
van Smaalen Sander,
Zörb Steffen,
Harbrecht Bernd
Publication year - 2012
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201200314
Subject(s) - van der waals force , superstructure , crystallography , intercalation (chemistry) , octahedron , vacancy defect , crystal structure , stacking , diffraction , materials science , crystal (programming language) , supercell , chemistry , inorganic chemistry , physics , molecule , thermodynamics , thunderstorm , programming language , organic chemistry , meteorology , computer science , optics
The eightfold 2a 0 ×2b 0 ×2c 0 superstructures of 6R‐Cu x Ta 1+ y S 2 are reported for crystal A with x = 0.237 and y = 0, and crystal B with x = 0.23 and y = 0.06. Compelling evidence is presented for the self‐intercalation of tantalum onto octahedral sites, based on the diffraction data and crystal chemical arguments. The eightfold superstructure is formed by partial vacancy ordering within planes of intercalated atoms, while the stacking of TaS 2 layers remains that of the 6R polytype. Temperature‐dependent X‐ray diffraction experiments show that the superstructure exists between T = 14 K and at least 370 K. Intercalated atoms enter the compound at octahedral and tetrahedral sites in alternating Van der Waals gaps. Intercalation is inhomogeneous, with average occupancies varying between 0.11 for octahedral sites within one Van der Waals gap and 0.23 for the tetrahedral sites within another Van der Waals gap. It is proposed that partial vacancy ordering is governed by the principle of maximum separation between intercalated atoms.