Long-range modulation of a composite crystal in a five-dimensional superspace
| Autor: | Pierre Fertey, Sylvain Ravy, Thomas Weber, Laurent Guérin, Michael Huard, Bo Wang, Philippe Rabiller, Stefan C. B. Mannsfeld, Shane M. Nichols, Céline Mariette, Mark D. Hollingsworth, Bertrand Toudic |
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| Rok vydání: | 2015 |
| Předmět: |
Physics
02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics Superspace 01 natural sciences Article Electronic Optical and Magnetic Materials Range (mathematics) Modulation Quantum mechanics 0103 physical sciences X-ray crystallography 010306 general physics 0210 nano-technology Composite crystal |
| Zdroj: | Physical Review B. 91 |
| ISSN: | 1550-235X 1098-0121 |
| DOI: | 10.1103/physrevb.91.184101 |
| Popis: | The intergrowth crystal of n-tetracosane/urea presents a misfit parameter, defined by the ratio γ = ch/cg (chost/cguest), that is very close to a commensurate value (γ ≅ 1/3). High-resolution diffraction studies presented here reveal an aperiodic misfit parameter of γ = 0.3369, which is found to be constant at all temperatures studied. A complex sequence of structural phases is reported. The high temperature phase (phase I) exists in the four-dimensional superspace group P6122(00γ). At Tc1 = 179(1) K, a ferroelastic phase transition increases the dimension of the crystallographic superspace. This orthorhombic phase (phase II) is characterized by the five-dimensional (5D) superspace group C2221(00γ)(10δ) with a modulation vector ao* + cm* = ao* + δ · ch*, in which the supplementary misfit parameter is δ = 0.025(1) in host reciprocal units. This corresponds to the appearance of a modulation of very long period (about 440 ± 16 Å). At Tc2 = 163.0(5) K, a 5D to 5D phase transition leads to the crystallographic superspace group P212121(00γ)(00δ) with a very similar value of δ. This phase transition reveals a significant hysteresis effect. |
| Databáze: | OpenAIRE |
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