Viscosity ofp-n-alkyloxycynnamic acids and statistical thermodynamic description of the nematic phase-isotropic liquid transition

2000 ◽  
Vol 34 (4) ◽  
pp. 356-359
Author(s):  
V. I. Klopov ◽  
I. V. Bagazhkov ◽  
S. A. Syrbu ◽  
G. G. Maidachenko
Keyword(s):  
Nematic Phase ◽  
Thermodynamic Description ◽  
Statistical Thermodynamic ◽  
Isotropic Liquid ◽  
Liquid Transition

Neutron Critical Scattering in the Nematic Phase and at the Nematic-Isotropic Liquid Transition in PAA

1981 ◽  
Vol 105 (1) ◽  
pp. K35-K37 ◽  
Author(s):  
A. Rajewska ◽  
A. Jabłonka ◽  
D. Sikorska ◽  
A. Sobaszek
Keyword(s):  
Nematic Phase ◽  
Isotropic Liquid ◽  
Liquid Transition

Thermodynamics of Defect Formation and Hydration of Y2O3

2012 ◽  
Vol 326-328 ◽  
pp. 126-131 ◽  
Author(s):  
L.P. Putilov ◽  
V.I. Tsidilkovski ◽  
A.N. Varaksin ◽  
Anatoly Yakovlevich Fishman
Keyword(s):  
Electronic Structure ◽  
Gas Phase ◽  
Defect Formation ◽  
Thermodynamic Description ◽  
Statistical Thermodynamic ◽  
Wide Range ◽  
F Center ◽  
Mechanical Approach ◽  
Quantum Mechanical Approach ◽  
F Centers

Defect formation in yttria with a small content of acceptor impurities in equilibrium with a hydrogen-containing gas phase is studied theoretically. A statistical-thermodynamic description of the yttriagas equilibrium is based on the approach developed for compounds with a complex electronic structure [Phys. Stat. Sol. B (1991) Vol. 168, p. 233]. The considered model of electronic structure for Y2O3 includes, besides valence and conduction bands, acceptor and F-center states. The energy of F-centers was calculated in the framework of the variational quantum-mechanical approach combined with the molecular statics method. It is shown that acceptor states appreciably affect the thermodynamics of defect formation, while the F-centers contribution in a wide range of external parameters is small. The concentrations of defects (protons, oxygen vacancies, electronic defects) and the Fermi level position are determined as functions of temperature and gas phase parameters.

scholarly journals ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 297 ◽  
Author(s):  
Aleksandra Drozd-Rzoska
Keyword(s):  
Relaxation Time ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Strong Electric Field ◽  
Low Frequency ◽  
Ionic Species ◽  
Crystalline Material ◽  
Isotropic Liquid ◽  
The Impact ◽  
Liquid Crystalline Material

Results of dielectric studies in the nematic and isotropic liquid phases of pentylcyanobiphenyl (5CB), a model rod-like liquid crystalline material, are shown. They are based on the discussion of the evolution of dielectric constant ( ε ), its changes under the strong electric field (nonlinear dielectric effect, NDE), and finally, the primary relaxation time. It is shown that changes in ε T and NDE are entirely dominated by the impact of pretransitional fluctuations (pre-nematic and pre-isotropic, respectively) which are associated with the weakly discontinuous character of the isotropic–nematic phase transition. This influence also extends for the low-frequency, ionic species dominated, region. Notable, that the derivative-based and distortions sensitive analysis revealed the tricritical nature of the I-N transition. Although the glass transition in 5CB occurs in the deeply supercooled state at T g ≈ − 68 ° C , the dynamics (changes of the primary relaxation time) follow a previtreous pattern both in the isotropic and in the nematic phase. Finally, the discussion of the ’molecular’ vs. ‘quasi-critical’ characterizations of the isotropic and nematic phases is presented. It shows the evident prevalence of the ‘quasi-critical-picture’, which offers the consistent temperature parameterization in the total tested temperature range.

scholarly journals Thermodynamic Formulations of Excess and Absolute Values of Adsorption on Solid Surfaces: A Comparison of One- and Two-Phase Approaches

1986 ◽  
Vol 3 (4) ◽  
pp. 271-291 ◽  
Author(s):  
H. Wittkopf ◽  
P. Bräuer
Keyword(s):  
High Pressures ◽  
Thermodynamic Description ◽  
Solid Surfaces ◽  
Statistical Thermodynamic ◽  
Two Phase ◽  
Phase Approach ◽  
Adsorption Analysis ◽  
Basic Concepts ◽  
The Difference ◽  
The One

The generally used methods of thermodynamic adsorption analysis are summarized in two basic concepts: the two-phase approach (which is an adequate picture of volume phase thermodynamics in adsorption) and the one-phase approach (which uses excess values for the thermodynamic description of adsorption). Differential and integral molar values of adsorption Δ a X̄ and Δ a X in the two-phase approach are not identical with the corresponding excess values Δ a X̄s and Δ a Xs in the one-phase approach. Especially at high temperatures and high pressures they may be entirely different. It is shown that the experimental methods most usually in adsorption thermodynamics (as adsorption volumetry and gravimetry) give excess data which are to be used in the one-phase approach but which can be transformed to the two-phase approach. Using statistical thermodynamic calculations the difference between these basic concepts is shown over a wide temperature range for the first virial coefficient, the internal energy and the heat capacity of adsorption.

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