Order parameter and packing studies in nematic and smectic A phases by x‐ray diffraction

1988 ◽  
Vol 89 (5) ◽  
pp. 3317-3322 ◽  
Author(s):  
W. Haase ◽  
Z. X. Fan ◽  
H. J. Müller
Keyword(s):  
Order Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Smectic A

scholarly journals Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

2009 ◽  
Vol 5 ◽  
Author(s):  
Gundula F Starkulla ◽  
Elisabeth Kapatsina ◽  
Angelika Baro ◽  
Frank Giesselmann ◽  
Stefan Tussetschläger ◽  
...  
Keyword(s):  
Terminal Group ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Maximum Phase ◽  
X Ray ◽  
Smectic A ◽  
Polar Groups ◽  
Chain Lengths ◽  
Mesomorphic Properties ◽  
Phase Width

Based on 5-(4-hydroxyphenyl)-2-octylpyrimidine 8, 5-phenylpyrimidine derivatives 3–7, 9 with different spacer chain lengths (C2 up to C6) and different terminal polar groups (Br, Cl, N3, OH, CN) were synthesized by etherification and nucleophilic substitution. The mesomorphic behaviour of these compounds was investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS and SAXS) and revealed smectic A mesophases for bromides, chlorides and azides 3, 4 and 6. For these compounds a maximum phase width was observed for the C5 spacer regardless of the terminal group, whereas the hydroxy- and cyano-substituted derivatives 5 and 7, respectively, were non mesomorphic and showed only melting transitions.

scholarly journals Smectic A: cholesteric phase transition investigated by small angle X-ray diffraction and viscosity measurements

2002 ◽  
Vol 32 (2b) ◽  
pp. 495-500 ◽  
Author(s):  
E. L. Duarte ◽  
R. Itri ◽  
A. R. Sampaio ◽  
M. Simões ◽  
A. J. Palangana
Keyword(s):  
Phase Transition ◽  
Small Angle ◽  
X Ray Diffraction ◽  
Cholesteric Phase ◽  
X Ray ◽  
Viscosity Measurements ◽  
Smectic A

Determination of the order parameter of CuPt-Bordered GaInP2 films by x-ray diffraction

2002 ◽  
Vol 91 (11) ◽  
pp. 9039-9042 ◽  
Author(s):  
J. H. Li ◽  
R. L. Forrest ◽  
S. C. Moss ◽  
Y. Zhang ◽  
A. Mascarenhas ◽  
...  
Keyword(s):  
Order Parameter ◽  
X Ray Diffraction ◽  
X Ray

Comparison of Simulated and Experimental Order Parameters in FePt—II

2011 ◽  
Vol 17 (3) ◽  
pp. 403-409 ◽  
Author(s):  
Karen L. Torres ◽  
Richard R. Vanfleet ◽  
Gregory B. Thompson
Keyword(s):  
Electron Diffraction ◽  
Order Parameter ◽  
Convergent Beam Electron Diffraction ◽  
Order Parameters ◽  
X Ray Diffraction ◽  
Chemical Order ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Convergent Beam ◽  
Good Agreement

AbstractEight FePt thin film specimens of various thicknesses, compositions, and order parameters have been analyzed to determine the robustness and fidelity of multislice simulations in determining the chemical order parameter via electron diffraction (ED). The shape of the simulated curves depends significantly on the orientation and thickness of the specimen. The ED results are compared to kinematical scattering order parameters, from the same films, acquired from synchrotron X-ray diffraction (XRD). For the specimens analyzed with convergent beam electron diffraction conditions, the order parameter closely matched the order parameter as determined by the XRD methodology. However, the specimens analyzed by selected area electron diffraction conditions did not show good agreement. This has been attributed to substrate effects that hindered the ability to accurately quantify the intensity values of the superlattice and fundamental reflections.

Small-angle x-ray diffraction study of mixtures showing re-entrant nematic phase and induced smectic Ad phase

1998 ◽  
Author(s):  
S. K. Giri ◽  
N. K. Pradham ◽  
R. Paul ◽  
S. Paul ◽  
P. Mandal ◽  
...  
Keyword(s):  
Diffraction Study ◽  
Small Angle ◽  
Nematic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Smectic A

The investigation of the microstructure and mechanical properties of ordered alominide-iron (boron) nanostructures produced by mechanical alloying and sintering

2012 ◽  
Vol 05 ◽  
pp. 488-495 ◽  
Author(s):  
S. Izadi ◽  
Gh. Akbari ◽  
K. Janghorban ◽  
M. Ghaffari
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Order Parameter ◽  
Fracture Strain ◽  
Sintering Temperature ◽  
Range Order Parameter ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
X Ray ◽  
Boron Nanostructures

In this study, mechanical alloying (MA) of Fe -50 Al , Fe -49.5 Al -1 B , and Fe -47.5 Al -5 B (at.%) alloy powders and mechanical properties of sintered products of the as-milled powders were investigated. X-ray diffraction (XRD) results showed the addition of B caused more crystallite refinement compared to the B -free powders. To consider the sintering and ordering behaviors of the parts produced from cold compaction of the powders milled for 80 h, sintering was conducted at various temperatures. It was found that the sintering temperature has no meaningful effect on the long-range order parameter. The transformation of the disordered solid solution developed by MA to ordered Fe - Al - ( B ) intermetallics was a consequence of sintering. Also, the nano-scale structure of the samples was retained even after sintering. The microhardness of pore-free zones of the nanostructured specimens decreased by increasing the sintering temperature. Moreover, the sintering temperature has no effect on the compressive yield stress. However, the fracture strain increased by increasing the sintering temperature. The samples containing 1 at.% B showed more strain to fracture compared with the B -free and 5 at.% B samples.

X-ray diffraction study of smectic A layering in terminally fluorinated liquid crystal materials

1993 ◽  
Vol 15 (3) ◽  
pp. 361-376 ◽  
Author(s):  
T. A. Lobko ◽  
B. I. Ostrovskii ◽  
A. I. Pavluchenko ◽  
S. N. Sulianov
Keyword(s):  
Liquid Crystal ◽  
Diffraction Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Smectic A ◽  
Liquid Crystal Materials

X-ray Diffraction Study of Chalcopyrite ZnSnP2 Epitaxial Layers

1999 ◽  
Vol 583 ◽  
Author(s):  
S. Francoeur ◽  
G. A. Seryogin ◽  
S. A. Nikishin ◽  
H. Temkin
Keyword(s):  
Order Parameter ◽  
Growth Conditions ◽  
Cation Sublattice ◽  
Crystallographic Structure ◽  
Epitaxial Layers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partially Ordered ◽  
Interesting Candidate

AbstractWe apply the technique of x-ray diffraction to the determination of the crystallographic structure and the quantitative measurement of the order parameter of ZnSnP2 epitaxial layers. In bulk, ZnSnP2 it is possible to obtain highly ordered distribution of Zn and Sn atoms in the cation sublattice, but epitaxial growth often produces partially ordered layers. The ordered and disordered phases correspond to the chalcopyrite and sphalerite structures and their respective band gaps are 1.66 and 1.24 eV. Since ZnSnP2 is almost lattice-matched to GaAs. it is interesting candidate for optoelectronic applications.Samples used in this work were grown by gas source molecular beam epitaxy on GaAs substrates. Slight variations in growth conditions could be induced to produce partially ordered and disordered structures. Chalcopyrite ordering is determined by the observation of several characteristic reflections identifying the lower symmetry of this structure. For example, reflections from (101), (217) and (611) planes, strictly forbidden for sphalerite, were measured. The quantitative determination of the order parameter could be made by comparing intensities of a carefully chosen set of measured and calculated reflections. We show that while kinematic approximation can be used to model weak superstructure reflections, in the calculation of the strong, low-angle, fundamental reflections used for intensity normalization it is necessary to take into account extinction effects. Order parameters varying from 0 to 30% were obtained.

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