FREEDERICKSZ-LIKE TRANSITIONS IN COMPENSATED NEMATIC LIQUID CRYSTALS

1991 ◽  
Vol 05 (04) ◽  
pp. 697-707
Author(s):  
G. BARBERO ◽  
L.R. EVANGELISTA ◽  
Z. GABBASOVA
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Liquid Crystals ◽  
Relative Phase ◽  
Nematic Liquid Crystals ◽  
Dielectric Anisotropy ◽  
Critical Fields ◽  
Inversion Point ◽  
Disorder Phase Transition ◽  
First Order

The occurrence of the Freedericksz transitions at the inversion point of the main dielectric anisotropy in nematic liquid crystals is discussed. It is shown that, if this kind of order-disorder phase transition can take place, they are always of the first order. The critical fields are evaluated, and the relative phase diagram is discussed.

Molecular Ordering in Nematic MBCA and EPAPU

1990 ◽  
Vol 45 (1) ◽  
pp. 29-32
Author(s):  
S. Sreehari Sastry ◽  
V. Venkata Rao ◽  
P. Narayana Murty ◽  
G. Satyanandam ◽  
T. F. Sundar Raj
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Order Parameter ◽  
Nematic Phase ◽  
Spin Probe ◽  
Nematic Liquid Crystals ◽  
Experimental Techniques ◽  
First Order ◽  
Molecular Ordering

AbstractBy EPR, two nematic liquid crystals (MBCA and EPAPU) were investigated using a steroidal nitroxide spin probe. In both liquid crystals the isotropic-nematic phase transition is of first order. The observed variation of the order parameter with temperature is compared with predictions from the Maier-Saupe and Humphries-James-Luckhurst models and with results obtained by several other experimental techniques.

TRICRITICAL POINT IN ORDER-DISORDER PHASE TRANSITIONS FOR NEMATICS

1992 ◽  
Vol 06 (14) ◽  
pp. 2521-2530 ◽  
Author(s):  
G. BARBERO ◽  
L. R. EVANGELISTA ◽  
A. P. KREKHOV
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Liquid Crystals ◽  
External Field ◽  
Tricritical Point ◽  
Nematic Liquid Crystals ◽  
Complete Analysis ◽  
Disorder Phase Transition ◽  
Anchoring Strength ◽  
Strong Anchoring

A complete analysis of the order-disorder phase transition in nematic liquid crystals induced by an external field is presented. The case of nearly compensated nematics in weak anchoring situation is discussed. The investigation shows that the parameter controlling the order of the phase transition is a decreasing function of the anchoring strength. The important limiting cases of very weak and very strong anchoring are considered too.

scholarly journals Notizen: Specific Volume Studies on Some Nematic Liquid Crystals

1975 ◽  
Vol 30 (8) ◽  
pp. 1094-1096 ◽  
Author(s):  
Birendra Bahadur
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Order Phase Transition ◽  
Specific Volume ◽  
Nematic Liquid Crystals ◽  
Adiabatic Compressibility ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase ◽  
Sudden Jump

Abstract The temperature variation of the specific volume of two nematic liquid crystals (HBT and OBT) has been observed in both the nematic and isotropic regions. A sudden jump is observed in the vicinity of the nematic-isotropic transition indicating a first order phase transition. Pretransitional effects are found to occur only on the nematic side of the transition. This accords with the Maier-Saupe theory. Some parameters such as SK , A, the adiabatic compressibility, the Rao number, and the van der Waals constant are also determined.

scholarly journals Emergence and stabilization of transient twisted defect structures in confined achiral liquid crystals at a phase transition.

Soft Matter ◽  
2021 ◽  
Author(s):  
Jose X Velez ◽  
Zhaofei Zheng ◽  
Daniel A. Beller ◽  
Francesca Serra
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Soft Matter ◽  
Capillary Tube ◽  
Nematic Liquid Crystals ◽  
Defect Structures

Spontaneous emergence of chirality is a pervasive theme in soft matter. We report a transient twist forming in achiral nematic liquid crystals confined to a capillary tube with square cross...

scholarly journals Electric properties of olive oil under pressure

2021 ◽  
Author(s):  
L. T. Pawlicki ◽  
R. M. Siegoczyński ◽  
S. Ptasznik ◽  
K. Marszałek
Keyword(s):  
Molecular Structure ◽  
Phase Transition ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Olive Oil ◽  
Material Parameters ◽  
First Order ◽  
Long Time ◽  
Capacitive Reactance ◽  
First Order Phase

AbstractThe main purpose of the experiment was a thermodynamic research with use of the electric methods chosen. The substance examined was olive oil. The paper presents the resistance, capacitive reactance, relative permittivity and resistivity of olive. Compression was applied with two mean velocities up to 450 MPa. The results were shown as functions of pressure and time and depicted on the impedance phase diagram. The three first order phase transitions have been detected. All the changes in material parameters were observed during phase transitions. The material parameters measured turned out to be the much more sensitive long-time phase transition factors than temperature. The values of material parameters and their dependence on pressure and time were compared with the molecular structure, arrangement of molecules and interactions between them. Knowledge about olive oil parameters change with pressure and its phase transitions is very important for olive oil production and conservation.

Temperature-triggered order–disorder phase transition in molecular-ionic material N-butyldiethanolammonium picrate monohydrate

RSC Advances ◽  
2016 ◽  
Vol 6 (73) ◽  
pp. 69546-69550 ◽  
Author(s):  
Tariq Khan ◽  
Muhammad Adnan Asghar ◽  
Zhihua Sun ◽  
Chengmin Ji ◽  
Lina Li ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Dielectric Materials ◽  
Disorder Phase Transition ◽  
First Order ◽  
Oxygen Atoms

We report an organic–ionic material that undergoes a first-order structural phase transition, induced by order–disorder of oxygen atoms in picrate anion. This strategy offers a potential pathway to explore new switchable dielectric materials.

INFLUENCE OF AN EXTERNAL MAGNETIC FIELD ON THE DYNAMICS OF A NEW-PHASE NUCLEUS IN THE VICINITY OF THE FIRST-ORDER PHASE TRANSITION IN MAGNETS WITH DEFECTS PRESENT

2012 ◽  
Vol 26 (28) ◽  
pp. 1250183 ◽  
Author(s):  
VLADIMIR NAZAROV ◽  
RISHAT SHAFEEV
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
External Magnetic Field ◽  
Magnetic Anisotropy ◽  
Spin Reorientation ◽  
Critical Fields ◽  
First Order ◽  
Phase Nucleus ◽  
First Order Phase Transition ◽  
New Phase

Theoretically, with the aid of a soliton model, the evolution of a new-phase nucleus near the first-order spin-reorientation phase transition in magnets has been investigated in an external magnetic field. The influence of an external field and one-dimensional defects of magnetic anisotropy on the dynamics of such nucleus has been demonstrated. The conditions for the localization of the new-phase nucleus in the region of the magnetic anisotropy defect and for its escape from the defect have been determined. The values of the critical fields which bring about the sample magnetization reversal have been identified and estimated.

Complex network structure of flocks in the Vicsek Model with Vectorial Noise

2014 ◽  
Vol 25 (03) ◽  
pp. 1350095 ◽  
Author(s):  
Gabriel Baglietto ◽  
Ezequiel V. Albano ◽  
Julián Candia
Keyword(s):  
Phase Transition ◽  
Complex Network ◽  
Network Structure ◽  
Time Step ◽  
Vicsek Model ◽  
Disorder Phase Transition ◽  
First Order ◽  
Direction Of Movement ◽  
Long Range Ordering ◽  
Influence Of Noise

In the Vicsek Model (VM), self-driven individuals try to adopt the direction of movement of their neighbors under the influence of noise, thus leading to a noise-driven order–disorder phase transition. By implementing the so-called Vectorial Noise (VN) variant of the VM (i.e. the VM-VN model), this phase transition has been shown to be discontinuous (first-order). In this paper, we perform an extensive complex network study of VM-VN flocks and show that their topology can be described as highly clustered, assortative, and nonhierarchical. We also study the behavior of the VM-VN model in the case of "frozen flocks" in which, after the flocks are formed using the full dynamics, particle displacements are suppressed (i.e. only rotations are allowed). Under this kind of restricted dynamics, we show that VM-VN flocks are unable to support the ordered phase. Therefore, we conclude that the particle displacements at every time-step in the VM-VN dynamics are a key element needed to sustain long-range ordering throughout.

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