The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds

Journal Article · Fri Sep 12 04:00:00 UTC 2014 · Zeitschrift fuer Kristallographie. Crystalline Materials

DOI: https://doi.org/10.1515/zkri-2014-1773 · OSTI ID:1280921

Mariette, Céline ^[1]; Guérin, Laurent ^[1]; Rabiller, Philippe ^[1]; Chen, Yu-Sheng ^[2]; Bosak, Alexei ^[3]; Popov, Alexander ^[3]; Hollingsworth, Mark D. ^[4]; Toudic, Bertrand ^[5]

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1. Univ. of Rennes, Rennes (France). Inst. of Physics
2. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
3. European Synchrotron Radiation Facility (ESRF), Grenoble (France)
4. Kansas State Univ., Manhattan, KS (United States). Dept. of Chemistry
5. Univ. of Rennes, Rennes (France). Campus de Beaulieu, Dept. of Physics

n-Dodecane/urea is a member of the prototype series of n-alkane/urea inclusion compounds. At room temperature, it presents a quasi-one dimensional liquid-like state for the confined guest molecules within the rigid, hexagonal framework of the urea host. At lower temperatures, we report the existence of two other phases. Below T_c=248 K there appears a phase with rank four superspace group P6₁22(00γ), the one typically observed at room temperature in n-alkane/urea compounds with longer guest molecules. A misfit parameter, defined by the ratio γ=c_h/c_g (c_host/c_guest), is found to be 0.632±0.005. Below T_c1=123 K, a monoclinic modulated phase is created with a constant shift along c of the guest molecules in adjacent channels. The maximal monoclinic space group for this structure is P12₁1(α0γ). We discuss analogies and differences with n-heptane/urea, which also presents a monoclinic, modulated low-temperature phase.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE; National Science Foundation (NSF)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1280921
• Journal Information: Zeitschrift fuer Kristallographie. Crystalline Materials, Journal Name: Zeitschrift fuer Kristallographie. Crystalline Materials Journal Issue: 1 Vol. 230; ISSN 2194-4946
• Publisher: De GruyterCopyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
alkane/urea crystals
aperiodic crystals
crystallographic superspace
diffraction
phase transitions