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Crystallography 2018
Structural Chemistry & Crystallography Communication
ISSN: 2470-9905
Page 41
June 04-05, 2018
London, UK
3
rd
Edition of International Conference on
Advanced Spectroscopy,
Crystallography and Applications
in Modern Chemistry
A
periodic composite crystals present long-range order without
translational symmetry. These materials may be described as
the intersection in three dimensions of a crystal which is periodic
in a higher-dimensional space. In such materials, symmetry
breaking must be described as structural changes within these
crystallographic superspaces. The increase in the number of
superspace groups with the increase in the dimension of the
superspace allows many more structural solutions. We will
present recent results obtained by complementary Laue neutron
diffraction and X-ray diffraction techniques on n-nonadecane-
urea, a nice illustration of aperiodic materials. Within this
original family of alkane-urea composites, we will illustrate
how structural phase transitions are characterized by changes
of intermodulation and described by increasing the rank of the
associated crystallographic superspaces.
Figure 1:
(a) Laue diffraction image of n-nonadecane–urea at T=170K (phase I)
(b) Expansion of the selected region of the diffraction
pattern at 170K
(b)
same area at 4K
Figure 2:
Phase diagram (T,P) of the fully deuterated n-nonadecane–urea [1,2]. All the
phases, I, II, III, IV and V, require a description within a crystallographic super-
space. Shaded region indicates the metastable region between the ordered
low-pressure and high-pressure phases. The two points associated with
TC3 mark the metastability limit between phase III and phase V [1]
Recent Publications
1. Zerdane S., Mariette C., Mc Intyre G., Lemée-Cailleau
M.H., Rabiller P., Guerin L., Ameline J.C., Toudic B.
(2015) Neutron Laue and X-ray diffraction study
of a new crystallographic superspace phase in
n-nonadecane-urea, Acta Cryst B71, 293-299
2. Toudic B., Rhabiller P., Bourgeois L., Huard M., Écolivet
C., Mc Intyre G., Bourges P., Breczewski T., Janssen T.
(2011) Temperature-pressure phase diagram of an
aperiodic host guest compound, Europhysics Letters
93, 16003-p1-5
3. Braunschweig H., Gackstatter A., Kupfer T., Radacki K.,
Franke S., Meyer K., Fucke K., Lemee-Cailleau M-H.
4. Uranium Hydridoborates: Synthesis, Magnetism, and
X-ray/Neutron Diffraction Structures, (2015) Inorganic
Chemistry 54/16, 8022-8028
NEUTRON LAUE AND X-RAY DIFFRACTION STUDY OF A NEW
CRYSTALLOGRAPHIC SUPERSPACE PHASE IN N-NONADECANE–UREA
Marie-Helene Lemee-Cailleau
Institut Laue Langevin, France
Marie-Helene Lemee-Cailleau, Struct Chem Crystallogr Commun 2018, Volume 4
DOI: 10.21767/2470-9905-C1-005