scholarly journals Static and Dynamic Properties of Ferroelectric Liquid Crystals in the Vicinity of a First-Order SmA-SmC* Phase Transition

1992 ◽  
Vol 47 (3) ◽  
pp. 536-542 ◽  
Author(s):  
Roland R. Netz ◽  
Siegfried Hess
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Order Parameter ◽  
Dynamic Properties ◽  
Theoretical Description ◽  
Deformation Tensor ◽  
Stationary Case ◽  
Angle Variation ◽  
Ferroelectric Liquid Crystals ◽  
First Order

AbstractA unified theoretical description of static and dynamic properties of ferroelectric liquid crystals in terms of a Landau free energy is presented. The shear deformation tensor is used as principal order parameter. Results for the stationary case for tilt angle variation and dielectric properties are compared with experiments on a compound with a pronounced first-order SmA-SmC* phase transition for various strengths of the applied electric field

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.

Order parameter fluctuations in ferroelectric liquid crystals

1991 ◽  
Vol 113 (1) ◽  
pp. 59-76 ◽  
Author(s):  
R. Blinc ◽  
M. Čopič ◽  
I. Drevenšek ◽  
A. Levstik ◽  
I. Muševič ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Order Parameter ◽  
Ferroelectric Liquid Crystals

scholarly journals Order Parameters, Orientational Distribution Functions and Heliconical Tilt Angles of Oligomeric Liquid Crystals

2019 ◽  
Author(s):  
Richard Mandle ◽  
John W. Goodby
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Tilt Angle ◽  
Order Parameter ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Thermal Evolution ◽  
Order Parameters ◽  
Distribution Functions ◽  
Orientational Distribution

We compare the order parameters, orientational distribution functions (ODF) and heliconical tilt angles of the TB phase exhibited by a liquid-crystalline dimer (CB7CB) to a tetramer (O47) and hexamer (O67) by SAXS/WAXS. Following the N-TB phase transition we find that all order parameters decrease, and while 〈P2 〉 remains positive 〈P4 〉 becomes negative. For all three materials the order parameter 〈P6 〉 is near zero in both phases. The ODF is sugarloaf-like in the nematic phase and volcano-like in the TB phase, allowing us to estimate the heliconical tilt angle of each material and its thermal evolution. The heliconical tilt angle appears to be largely independent of the material studied despite the differing number of mesogenic units.

TEMPERATURE DEPENDENCE OF SURFACE TENSION OF LIQUID CRYSTALS AT THE PHASE TRANSITION

1995 ◽  
Vol 09 (03n04) ◽  
pp. 237-242 ◽  
Author(s):  
R. MOLDOVAN ◽  
M. TINTARU ◽  
T. BEICA ◽  
S. FRUNZA ◽  
D. N. STOENESCU
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Surface Tension ◽  
Free Energy ◽  
Surface Layer ◽  
Order Parameter ◽  
Unit Area ◽  
Negative Slope ◽  
First Order ◽  
First Order Transition

The surface tension is calculated as the excess of the free energy per unit area, due to the presence of a surface layer, using Landau–de Gennes expansions, in the hypothesis of a first order transition in the bulk and taking into account the dependence of the surface free energy from the surface tilt angle. The surface order parameter is calculated and surface-ordered phase above the phase transition temperature has been found. A variety of calculated surface tension versus temperature curves with a jump at the phase transition, with positive or negative slope, well describing the experimental data from literature, have been attained.

Static and dynamical elastic behavior of Lu5Ir4Si10 around its first-order structural phase transition

2020 ◽  
Vol 34 (12) ◽  
pp. 2050116
Author(s):  
M. Saint-Paul ◽  
C. Opagiste ◽  
C. Guttin
Keyword(s):  
Phase Transition ◽  
Theoretical Approach ◽  
Order Parameter ◽  
Landau Theory ◽  
Structural Phase ◽  
Elastic Stiffness ◽  
Elastic Behavior ◽  
Velocity Measurements ◽  
First Order ◽  
First Order Transition

Ultrasonic velocity measurements could be performed on a good quality single crystal of [Formula: see text] around its transition around 80 K. The behavior of the stiffness components demonstrates a first-order transition. The temperature dependence of the longitudinal elastic stiffness components [Formula: see text] and [Formula: see text] can be analyzed by the classical Landau theory and assuming a stricter coupling between the strain and the order parameter. A theoretical approach and experimental results are discussed.

scholarly journals Image Analysis Studies for Phase Transitions of Ferroelectric Liquid Crystals

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
S. Sreehari Sastry ◽  
B. Gowri Sankara Rao ◽  
K. B. Mahalakshmi ◽  
K. Mallika ◽  
C. Nageswara Rao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Image Analysis ◽  
Liquid Crystals ◽  
Optical Microscope ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Statistical Parameters ◽  
Ferroelectric Liquid Crystals ◽  
Phase Transition Temperatures ◽  
Parameter Values

Phase transition temperatures of ferroelectric liquid crystals ((S)-(-)-2-methylbutyl 4′-(4″-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (where n=16 and 18)) are studied through two techniques of image analysis. One is a statistical method, applied to compute the statistical parameters from the textures of each sample and the other, computation of Legendre moments being applied as image moment analysis, both of which are considered as a function of temperature. The textures of the samples are recorded with the polarizing optical microscope (POM) attached to the hot stage and high resolution camera. The phase transition temperatures of samples are inferred by the abrupt changes in the computed parameter values. The results obtained from the present methodology are in good agreement with those published in earlier literature done by the different techniques, like differential scanning calorimetry (DSC).

A FIRST ORDER PHASE TRANSITION IN ISING FERRIMAGNETS

1995 ◽  
Vol 09 (21) ◽  
pp. 1347-1351 ◽  
Author(s):  
HASAN M. AL MUKADAM ◽  
DIMO I. UZUNOV
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Mean Field Theory ◽  
Mean Field ◽  
First Order ◽  
First Order Phase Transition ◽  
Exchange Constants ◽  
The Mean ◽  
First Order Phase ◽  
Ising Spins

The mean field theory is used for the analysis of a two-sublattice system of Ising spins, which describes ferro-, antiferro-, and ferrimagnetic orderings. It is proven that the phase transition in these systems is of a first order when the exchange constants of the sublattices are different. The free energy, the order parameter profiles and the latent heat of the phase transition are calculated for almost equivalent sublattices.

Sign in / Sign up

Export Citation Format

Share Document