TY - JOUR
T1 - Modular crystals as modulated structures
T2 - the case of the lillianite homologous series
AU - Elcoro, L.
AU - Perez-Mato, J.M.
AU - Friese, K.
AU - Petricek, V.
AU - Balic Zunic, Tonci
AU - Olsen, L.A.
PY - 2008
Y1 - 2008
N2 - The use of the superspace formalism is extended to the description and refinement of the homologous series of modular structures with two symmetry-related modules with different orientations. The lillianite homologous series has been taken as a study case. Starting from a commensurate modulated composite description with two basic subsystems corresponding to the two different modules, it is shown how a more efficient description can be achieved using so-called zigzag modulation functions. These linear zigzag modulations, newly implemented in the program JANA2006, have very large fixed amplitudes and introduce in the starting model the two orientations of the underlying module sublattices. We show that a composite approach with this type of function, which treats the cations and anions as two separate subsystems forming a misfit compound, is the most appropriate and robust method for the refinements.
AB - The use of the superspace formalism is extended to the description and refinement of the homologous series of modular structures with two symmetry-related modules with different orientations. The lillianite homologous series has been taken as a study case. Starting from a commensurate modulated composite description with two basic subsystems corresponding to the two different modules, it is shown how a more efficient description can be achieved using so-called zigzag modulation functions. These linear zigzag modulations, newly implemented in the program JANA2006, have very large fixed amplitudes and introduce in the starting model the two orientations of the underlying module sublattices. We show that a composite approach with this type of function, which treats the cations and anions as two separate subsystems forming a misfit compound, is the most appropriate and robust method for the refinements.
KW - Faculty of Science
KW - modulated structures
KW - misfit compound
KW - superspace formalism
KW - homologous series
U2 - 10.1107/s0108768108031492
DO - 10.1107/s0108768108031492
M3 - Journal article
SN - 2052-5192
VL - 64
SP - 684
EP - 701
JO - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
JF - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
IS - 6
ER -