Two-order-parameter phenomenological theory of the phase diagram of liquid helium

1996 ◽  
Vol 53 (13) ◽  
pp. 8583-8590
Author(s):  
Partha Goswami ◽  
K. K. Singh
Keyword(s):  
Phase Diagram ◽  
Liquid Helium ◽  
Order Parameter ◽  
Phenomenological Theory

scholarly journals Bicritical Central Point of Ising Model Phase Diagram

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Yahia Boughaleb ◽  
Mohammed Nouredine ◽  
Mohamed Snina ◽  
Rachid Nassif ◽  
Mohamed Bennai
Keyword(s):  
Phase Diagram ◽  
Order Parameter ◽  
Present Model ◽  
Central Point ◽  
Square Lattice ◽  
Ordered Structures ◽  
Ordered Phases ◽  
Algebraic Order ◽  
Pure Phases ◽  
Model Phase

We deal with a 2D half occupied square lattice with repulsive interactions between first and second neighboring particles. Despite the intensive studies of the present model the central point of the phase diagram for which the ratio of the two interaction strengths is still open. In the present paper we show, using standard Monte Carlo calculations, that the situation corresponds to a phase of mixed ordered structures quantified by an “algebraic” order parameter defined as the sum of densities of the existing ordered clusters. The introduced grandeur also characterizes the transitions towards the known pure ordered phases for the other values of as mentioned by the agreement of our results with those of the literature. The computation of the Cowley short range order parameter against suggests that the central point is bicritical and is a state to cross when passing between the two pure phases.

Phenomenological theory of the superconductivity phase diagram ofU1−xThxBe13

1989 ◽  
Vol 39 (4) ◽  
pp. 2200-2216 ◽  
Author(s):  
Manfred Sigrist ◽  
T. M. Rice
Keyword(s):  
Phase Diagram ◽  
Phenomenological Theory

Phenomenological theory of the temperature-composition phase-diagram in the magnetic system TbGe1-xSix

1988 ◽  
Vol 79 (1) ◽  
pp. 83-86 ◽  
Author(s):  
P. Schobinger-Papamantellos ◽  
K. H. J. Buschow ◽  
F. Maaroufi ◽  
P. Toledano
Keyword(s):  
Phase Diagram ◽  
Magnetic System ◽  
Phenomenological Theory

A MEAN FIELD STUDY OF THE PHASE TRANSITIONS IN A CLASS OF SYSTEMS WITH COMPLEX ORDER PARAMETERS

1994 ◽  
Vol 08 (28) ◽  
pp. 3963-3986
Author(s):  
EVGENIA J. BLAGOEVA
Keyword(s):  
Phase Diagram ◽  
Phase Transitions ◽  
Order Parameter ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Unconventional Superconductors ◽  
Complex Order ◽  
The Mean ◽  
Expansion Coefficients

A generalized Landau free energy for a complex order parameter expanded up to sixth-order is investigated using group theoretical arguments and the mean-field approximation. Results for the phase transitions that occur are presented. The phase diagram for all allowed values of the expansion coefficients is constructed with an emphasis placed on the influence of the anisotropy in the order parameter space. The results can be used in discussions of unconventional superconductors and modulated structural and magnetic orderings.

Calculation of the (GaAs)m(AlAs)n Superlattice Piezoelectric Constants

1994 ◽  
Vol 356 ◽  
Author(s):  
Vadim. Yu. Mirovitskii
Keyword(s):  
Phase Transitions ◽  
Order Parameter ◽  
Thermodynamic Potential ◽  
Mixed Crystal ◽  
Piezoelectric Properties ◽  
Phenomenological Theory ◽  
Initial Structure ◽  
Spatial Correlations ◽  
Specific Calculations ◽  
Piezoelectric Constants

AbstractA new method for calculation of superlattice (SL) piezoelectric properties is proposed. It is used for derivation of the piezoelectric constants of ultrathin [001] oriented (GaAs)m(AlAs)n SL. These SL are formally considered to result from complete ordering Ga (Al) atoms over a-positions of a hypothetical initial structure of a bulk mixed crystal of (GaxAl1-x)As with x=m/(m+n). This viewpoint allows us to develop a method which is close to the Landau phenomenological theory of second- order phase transitions and which is intended for calculation of the SL crystal-lophysical constants. It is shown that a nontrivial term has much significance in changing one of the piezoelectric constants, γz,xy, when the initial structure is transformed into a SL. This term is composed of coefficients at three translational invariants (Dzyaloshinskii invariants) in the expansion of the thermodynamic potential of the “ordering” system in a power series of the order parameter components. The values of these coefficients must be obtained from microscopic calculations which take account of spatial correlations in Ga(Al) atomic distribution. Specific calculations are carried out for a SL with m+n=3.

scholarly journals Структурные механизмы и термодинамическое описание изосимметрийного орбитального упорядочения в редкоземельных манганитах

2019 ◽  
Vol 61 (11) ◽  
pp. 2056
Author(s):  
М.П. Ивлиев ◽  
В.П. Сахненко
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Phenomenological Theory ◽  
Internal Field ◽  
Orbital Ordering ◽  
Entire Series ◽  
Cubic Lattice ◽  
Orbital Phase ◽  
Jahn Teller ◽  
Jahn Teller Effect

It is shown that the observed features of the orbital phase transition in AMnO3 perovskites (A = La, Pr, ..., Lu) are due to the occurrence of rotational distortions of a cubic lattice at high temperatures, causing anion displacements that create an “internal field” which, by symmetry, coincides with the order parameter describing the ordering of octahedra distorted due to the Jahn-Teller effect (orbital ordering). The influence of this “field” essentially determines the type of orbital ordering, its temperature and the nature of the phase transition. A comparative analysis of orbitally ordered states was carried out for the entire series of AMnO3, both in the framework of the phenomenological theory of phase transitions and on the basis of the three-minimum multi-lattice model proposed in the article. The specific features of the magnetic transitions in manganites, due to the specific features of the structure, are discussed.

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