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Structural Synthon Approach to Predict the Possible Polytypes of Layered Double Hydroxides
Author(s) -
Radha S.,
Kamath P. Vishnu
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.201200261
Subject(s) - synthon , stacking , monoclinic crystal system , crystallography , symmetry (geometry) , symmetry operation , yield (engineering) , materials science , group (periodic table) , crystal structure , chemistry , stereochemistry , geometry , mathematics , composite material , organic chemistry
Abstract The complete universe of possible polytypes of layered double hydroxides (LDH) is predicted on the basis of symmetry arguments. A single [MX 2 ] (X = OH) layer, also defined as a structural synthon, belongs to the layer group P $\bar{3}$ 2/ m 1. These layers can be stacked in such a way as to conserve the unique 3‐axis of the layer in the resultant crystal. The different stacking sequences that facilitate symmetry conservation, yield the different possible polytypes of rhombohedral and hexagonal symmetries. More polytypes can be envisaged by including stacking sequences that systematically destroy the principal symmetry elements of the structural synthon. Thereby, stacking sequences that destroy the 3‐axis, while retaining the 2‐axis, yield possible polytypes of monoclinic symmetry. The nitrate‐containing LDH of zinc and aluminum crystallizes in a faulted structure in which, the planar faults are shown to arise on account of stacking sequences whose local symmetry is monoclinic. This approach to polytype prediction expands on an earlier reported method by Bookin and Drits and is very general with important implications for other classes of layered materials.