Calculation of the tilt angle and susceptibility for the α–β transition in quartz using a mean field model

2017 ◽  
Vol 31 (09) ◽  
pp. 1750092 ◽  
Author(s):  
H. Yurtseven ◽  
U. Ipekoğlu ◽  
S. Ateş
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Tilt Angle ◽  
Phenomenological Model ◽  
Order Parameter ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
The Mean

Tilt angle (order parameter) and the susceptibility are calculated as a function of temperature for the [Formula: see text]–[Formula: see text] transition in quartz using a Landau phenomenological model. The tilt angle as obtained from the model is fitted to the experimental data from the literature and the temperature dependence of the tilt angle susceptibility is predicted close to the [Formula: see text]–[Formula: see text] transition in quartz. Our results show that the mean field model explains the observed behavior of the [Formula: see text]–[Formula: see text] phase transition in quartz adequately and it can be applied to some related materials.

Calculation of the Spontaneous Polarization and the Dielectric Constant for the Ferroelectric N(CH3)4HSO4 Using the Mean Field Model

2017 ◽  
Vol 36 (9) ◽  
pp. 863-869
Author(s):  
H. Yurtseven ◽  
M. Celik ◽  
H. Karacali
Keyword(s):  
Experimental Data ◽  
Dielectric Constant ◽  
Spontaneous Polarization ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Temperature Dependences ◽  
Inverse Susceptibility ◽  
The Mean ◽  
Fitting Parameters

AbstractThe temperature dependences of the spontaneous polarization and the dielectric constant (susceptibility) are calculated using the mean field model for the ferroelectric N(CH3)4HSO4. Expressions derived from the mean field model for the spontaneous polarization and the inverse susceptibility are fitted to the experimental data from the literature. The fitting parameters in the expansion of the free energy in terms of the spontaneous polarization are determined within the temperature intervals in the ferroelectric and paraelectric phases of N(CH3)4HSO4. Our results show that the temperature dependences of the spontaneous polarization and the dielectric constant as predicted from our mean field model, describe adequately the observed behavior of N(CH3)4HSO4 in the ferroelectric and paraelectric phases.

scholarly journals Phase transitions of quasistationary states in the Hamiltonian Mean Field model

Open Physics ◽  
2012 ◽  
Vol 10 (3) ◽  
Author(s):  
Pierre Buyl ◽  
Duccio Fanelli ◽  
Stefano Ruffo
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Field Model ◽  
Equilibrium Phase ◽  
Mean Field ◽  
Correct Order ◽  
Mean Field Model ◽  
Equilibrium Dynamics ◽  
Equilibrium Phase Transition ◽  
Negative Susceptibility

AbstractThe out-of equilibrium dynamics of the Hamiltonian Mean Field (HMF) model is studied in presence of an externally imposed magnetic field h. Lynden-Bell’s theory of violent relaxation is revisited and shown to adequately capture the system dynamics, as revealed by direct Vlasov based numerical simulations in the limit of vanishing field. This includes the existence of an out-of-equilibrium phase transition separating magnetized and non magnetized phases. We also monitor the fluctuations in time of the magnetization, which allows us to elaborate on the choice of the correct order parameter when challenging the performance of Lynden-Bell’s theory. The presence of the field h removes the phase transition, as it happens at equilibrium. Moreover, regions with negative susceptibility are numerically found to occur, in agreement with the predictions of the theory.

The mean field model withP2θ2coupling for the smectic A-smectic C* phase transition in liquid crystals

1998 ◽  
Vol 66 (1-4) ◽  
pp. 259-270 ◽  
Author(s):  
S. SalihoĞLu ◽  
H. Yurtseven ◽  
A. Giz ◽  
D. Kayişoğlu ◽  
A. Konu
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Smectic A ◽  
Smectic C ◽  
The Mean

TILT ANGLE AND THE TEMPERATURE SHIFTS CALCULATED AS A FUNCTION OF CONCENTRATION FOR THE AC* PHASE TRANSITION IN A BINARY MIXTURE OF LIQUID CRYSTALS

2011 ◽  
Vol 25 (13) ◽  
pp. 1791-1806 ◽  
Author(s):  
H. YURTSEVEN ◽  
M. KURT
Keyword(s):  
Phase Transition ◽  
Free Energy ◽  
Liquid Crystals ◽  
Binary Mixture ◽  
Tilt Angle ◽  
Field Model ◽  
Mean Field ◽  
Temperature Shift ◽  
Mean Field Model ◽  
Mean Field Models

We study here the tilt angle and the temperature shifts as a function of concentration for the AC* phase transition in a binary mixture, using our mean field model with the biquadratic P2θ2 coupling — and also with the bilinear Pθ and P2θ2 couplings. By expanding the free energy in terms of the tilt angle and polarization, the tilt angle and the temperature shift are evaluated by using the coefficients given in the free energy expansion. By employing a concentration-dependent coefficient, the tilt angle and the temperature shift are calculated as a function of concentration of 10.O.4 for the SmAC* transition in a binary mixture of C7 and 10.O.4. Our calculated values of the tilt angle and the temperature shifts decrease as the concentration of 10.O.4 increases, as confirmed experimentally for the AC* transition in this binary mixture. This indicates that our mean field models studied here are satisfactory to explain the observed behavior of the AC* transition of the binary mixture of C7 and 10.O.4.

scholarly journals Relativistic selfinteracting particle­-antiparticle system of bosons

2020 ◽  
Vol 28 (2) ◽  
pp. 3-18
Author(s):  
D. Anchishkin ◽  
V. Gnatovskyy ◽  
D. Zhuravel ◽  
V. Karpenko
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
Specific Heat ◽  
Temperature Interval ◽  
Thermodynamic Functions ◽  
Field Model ◽  
Mean Field ◽  
Einstein Condensate ◽  
Mean Field Model ◽  
The Mean

Thermodynamic properties of a system of an interacting boson particles and antiparticles at high tem­peratures are studied within the framework of the thermodynamically consistent Skyrme-­like mean-­field model. The mean field contains both attractive and repulsive terms. Self­-consistency relations between the mean field and thermodynamic functions are derived. We assume a conservation of the isospin density for all temperatures. It is shown that, independently of the strength of the attractive mean field, at the critical tem­perature Tc the system undergoes the phase transition of second order to the Bose­-Einstein condensate, which exists in the temperature interval 0 ≤ T ≤ Tc . It is obtained that the condensation represents a discontinuity of the derivative of the specific heat at T = Tc .

Single-Crystal Magnetic Properties of [Co(NH3)5(OH2)] [Cr(CN)6] Between 2 and 300 K

1992 ◽  
Vol 45 (11) ◽  
pp. 1899 ◽  
Author(s):  
PA Reynolds ◽  
CD Delfs ◽  
BN Figgis ◽  
B Moubaraki ◽  
KS Murray
Keyword(s):  
Ising Model ◽  
Field Model ◽  
Mean Field ◽  
Zero Field ◽  
Spin Orbit Coupling ◽  
Zero Field Splitting ◽  
Magnetic Exchange Interaction ◽  
Mean Field Model ◽  
Magnetic Exchange ◽  
The Mean

The magnetic susceptibilities along and perpendicular to the c axis (hexagonal setting) between 2.0 and 300 K at a magnetic field of 1.00 T, and the magnetizations at field strengths up to 5.00 T, are presented for single crystals of [Co(NH3)5(OH2)] [Cr(CN)6]. The results are interpreted in terms of zero-field splitting (2D) of the ground 4A2g term by spin-orbit coupling and of magnetic exchange interaction between the chromium atoms. The magnetic exchange is modelled as one of Ising or mean-field in type. The exchange is found to be quite small: J = -0.18(6) cm-1 if the Ising model is employed, and -0.03(1) cm-1 for the mean-field model. The model adopted for the exchange has a strong influence on the value of the parameter D obtained. When the Ising model is used D is deduced to be -0.28(9) cm-l; when the mean-field model is used D is -0.14(4) cm-l. The g-values deduced are in agreement with those from e.s.r. measurements at higher temperatures and do not depend on the exchange model. In any case, D is found to be sufficiently large that it must be considered in a polarized neutron diffraction experiment on the compound.

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