Orientational order–disorder transitions in solid hydrogen

1988 ◽  
Vol 66 (4) ◽  
pp. 908-914 ◽  
Author(s):  
N. S. Sullivan
Keyword(s):  
Orientational Order ◽  
Para Hydrogen ◽  
Local Ordering ◽  
Molecular Alignments ◽  
Hydrogen Mixtures ◽  
The Mean ◽  
Orientational Ordering ◽  
Quantum Rotors ◽  
Long Range Ordering ◽  
Continuous Freezing

We discuss the orientational ordering in solid ortho–para hydrogen mixtures. Following a brief sketch of the properties of the ortho and para hydrogen modifications and the long-range ordering of an assembly of J = 1 quantum rotors (ortho-H2), we consider the nature of the purely local ordering seen in random dilute ortho–para mixtures. Measurements of the quasi-static glass order parameter and the mean correlation time for the molecular alignments are interpreted in terms of a rapid but continuous freezing of the orientational fluctuations.

Local ordering in dilute ortho-para-hydrogen mixtures at low temperatures

1988 ◽  
Vol 72 (1-2) ◽  
pp. 1-24 ◽  
Author(s):  
C. M. Edwards ◽  
D. Zhou ◽  
Y. Lin ◽  
N. S. Sullivan
Keyword(s):  
Low Temperatures ◽  
Para Hydrogen ◽  
Local Ordering ◽  
Hydrogen Mixtures

Orientational ordering in solid hydrogen

1987 ◽  
Vol 65 (11) ◽  
pp. 1463-1470 ◽  
Author(s):  
N. S. Sullivan ◽  
C. M. Edwards ◽  
Y. Lin ◽  
D. Zhou
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Solid Hydrogen ◽  
Order Parameters ◽  
Para Hydrogen ◽  
Hydrogen Mixtures ◽  
Orientational Ordering ◽  
Nuclear Magnetic

The orientational ordering in solid ortho–para hydrogen mixtures is reviewed with emphasis on dilute mixtures for which a glass-like freezing of the randomly distributed quantum rotators is observed. The interpretation of the various nuclear magnetic resonance experiments used to monitor the relevant order parameters is discussed, and a summary is given of the current consensus and outstanding problems concerning the nature of the ordering in random dilute mixtures.

The orientational ordering of solute molecules in nematic solvents: cyanobenzenes, bromobenzenes, and p-benzoquinone in EBBA and 1132

1990 ◽  
Vol 68 (6) ◽  
pp. 875-880 ◽  
Author(s):  
C. T. Yim ◽  
D. F. R. Gllson
Keyword(s):  
Liquid Crystals ◽  
Potential Energy ◽  
Electric Field Gradient ◽  
Short Range ◽  
Orientational Order ◽  
Short Range Interaction ◽  
Range Interaction ◽  
Average Electric Field ◽  
Orientational Ordering ◽  
Shape And Size

The orientational order parameters of benzonitrile and o-, m-, and p-dicyanobenzene, monobromo- and p-dibromobenzene, and p-benzoquinone, dissolved in two nematic solvents, 1132 and EBBA, have been measured as functions of temperature, and used to determine the potential energy parameters for each solute–solvent pair. These parameters have been correlated with a short-range interaction based upon a shape and size function of the solute molecule and a long-range contribution due to the interaction between the solute molecular quadrupole moment and the average electric field gradient. Keywords: nematic liquid crystals, orientational ordering of solutes.

Molecular Polarizabilities and Orientational Ordering of Two Mesogens

1991 ◽  
Vol 46 (10) ◽  
pp. 858-864 ◽  
Author(s):  
M. Mitra ◽  
S. Paul ◽  
R. Paul
Keyword(s):  
Field Theory ◽  
Liquid Crystalline ◽  
Mean Field Theory ◽  
Orientational Order ◽  
Mean Field ◽  
Continuum Theory ◽  
Order Parameters ◽  
Liquid Phases ◽  
Molecular Polarizabilities ◽  
The Mean

AbstractThe refractive indices (no, ne) and densities of two mesogens have been measured in their liquid crystalline and liquid phases. The molecular polarizabilities (xo, xe) were evaluated by Vuks' and Neugebauer's relations. The polarizabilities thus obtained are compared with those estimated from the bond polarizabilities, and the orientational order parameters, <P2>, are compared with the mean field theory of Maier and Saupe, the modified mean field theory of Humphries, James and Luckhurst. and the continuum theory suggested by T. E. Faber. We have also calculated the three order parameters (<P2), τ, σ) describing the smectic A phase following McMillan's model. Possible causes of the discrepancy are discussed.

scholarly journals Electro-induced orientational ordering of anisotropic pigment nanoparticles

2013 ◽  
Vol 371 (1988) ◽  
pp. 20120257 ◽  
Author(s):  
Robert J. Greasty ◽  
Robert M. Richardson ◽  
Susanne Klein ◽  
David Cherns ◽  
Michael R. Thomas ◽  
...  
Keyword(s):  
Electric Fields ◽  
Orientational Order ◽  
Optical Response ◽  
Pigment Particle ◽  
X Ray ◽  
X Ray Scattering ◽  
Orientational Ordering ◽  
Nematic Phases ◽  
High Concentrations ◽  
Ray Scattering

The response of anisotropic pigment particle suspensions to externally applied electric fields has been explored for possible application in reflective display technologies. Three different types of pigment particle were suspended in dodecane, using a polymeric stabilizer, and showed Schlieren textures between crossed polarizers at high concentrations (greater than 25–30 wt%), indicating the formation of colloidal nematic phases. Orientational order parameters were determined by X-ray scattering, and the influence of polydispersity on the values is discussed. X-ray scattering measurements also demonstrated a change in the structure factor consistent with the onset of a colloidal nematic phase. In addition, the pigment particles were dispersed into various liquid crystal hosts at low concentrations (less than 5 wt%) with and without the presence of mesogenic mimic stabilizers. However, the influence of these stabilizers on orientational ordering could not be confirmed. The electro-induced ordering determined via scattering was related to the electro-optical response of each suspension using a simple model. The particles in nematic hosts not only showed a high degree of orientational ordering at lower electric field strengths, but also showed a reduction in stability. Although these systems have shown strong orientational ordering, the optical response has been limited by the intrinsic shape of the pigment particles and the distribution of the transition dipoles moments within them. Nevertheless, the feasibility of developing materials for display applications has been demonstrated.

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