scholarly journals Formation of complex radiation defects in irradiated materials

2021 ◽  
Vol 65 (3) ◽  
pp. 275-280
Author(s):  
V. A. Labunov ◽  
N. T. Kvasov ◽  
V. I. Yarmolik ◽  
E. R. Pavlovskaya
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Order Parameter ◽  
Experimental Results ◽  
Radiation Defects ◽  
Vacancy Defects ◽  
Disorder Phase Transition ◽  
Elastic Stresses ◽  
Initial Crystal ◽  
Drift Component

The principles of formation of the complex vacancy defects (V-clusters), their ensembles and patterns of formation of superlattices of the V-clusters are determined. The inclusion of the drift component of the elementary defects into the field of elastic stresses of the V-cluster in the analysis allowed describing its genesis and development adequately. The mechanisms of motion of the V-clusters in the material are described in detail, considering their interaction with each other. The authors have developed the original physical and mathematical formalism within which it has become possible to describe the order-disorder phase transition when an ensemble of clusters chaotically distributed in the irradiated solid transforms into an ordered coherent superlattice. The critical point of the phase transition and the parameters of the defect lattice itself are determined. They are confirmed by the experimental results. The ordering process in this system is understood as the motion of the undamped wave of order parameter through the material, while other configuration states of the V-cluster ensemble constitute rapidly damping fluctuations. The article also shows the mechanism of linking the symmetry of the V-cluster superlattice to the symmetry of the initial crystal.

scholarly journals Generalized Independence in the q-Voter Model: How Do Parameters Influence the Phase Transition?

Entropy ◽  
2020 ◽  
Vol 22 (1) ◽  
pp. 120 ◽  
Author(s):  
Angelika Abramiuk ◽  
Katarzyna Sznajd-Weron
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Broad Spectrum ◽  
Order Parameter ◽  
Analytical Formula ◽  
Voter Model ◽  
Pair Approximation ◽  
Scaling Relation ◽  
Independent Behavior

We study the q-voter model with flexibility, which allows for describing a broad spectrum of independence from zealots, inflexibility, or stubbornness through noisy voters to self-anticonformity. Analyzing the model within the pair approximation allows us to derive the analytical formula for the critical point, below which an ordered (agreement) phase is stable. We determine the role of flexibility, which can be understood as an amount of variability associated with an independent behavior, as well as the role of the average network degree in shaping the character of the phase transition. We check the existence of the scaling relation, which previously was derived for the Sznajd model. We show that the scaling is universal, in a sense that it does not depend neither on the size of the group of influence nor on the average network degree. Analyzing the model in terms of the rescaled parameter, we determine the critical point, the jump of the order parameter, as well as the width of the hysteresis as a function of the average network degree ⟨ k ⟩ and the size of the group of influence q.

scholarly journals A new type of non-Hermitian phase transition in open systems far from thermal equilibrium

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
T. T. Sergeev ◽  
A. A. Zyablovsky ◽  
E. S. Andrianov ◽  
A. A. Pukhov ◽  
Yu. E. Lozovik ◽  
...  
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Energy Flow ◽  
Thermal Equilibrium ◽  
Order Parameter ◽  
Open Systems ◽  
Coupled Systems ◽  
Exceptional Point ◽  
Relaxation Rates ◽  
New Type

AbstractWe demonstrate a new type of non-Hermitian phase transition in open systems far from thermal equilibrium, which can have place in the absence of an exceptional point. This transition takes place in coupled systems interacting with reservoirs at different temperatures. We show that the spectrum of energy flow through the system caused by the temperature gradient is determined by the $$\varphi^{4}$$ φ 4 -potential. Meanwhile, the frequency of the maximum in the spectrum plays the role of the order parameter. The phase transition manifests itself in the frequency splitting of the spectrum of energy flow at a critical point, the value of which is determined by the relaxation rates and the coupling strength. Near the critical point, fluctuations of the order parameter diverge according to a power law with the critical exponent that depends only on the ratio of reservoirs temperatures. The phase transition at the critical point has the non-equilibrium nature and leads to the change in the energy flow between the reservoirs. Our results pave the way to manipulate the heat energy transfer in the coupled out-of-equilibrium systems.

Order–disorder phase transition in FeAl alloys by neutron diffraction

1982 ◽  
Vol 60 (9) ◽  
pp. 1323-1327 ◽  
Author(s):  
N. Ahmed ◽  
N. M. Butt ◽  
M. M. Beg ◽  
J. Aslam ◽  
Q. H. Khan ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Neutron Diffraction ◽  
Order Parameter ◽  
Critical Index ◽  
Feal Alloy ◽  
Disorder Phase Transition ◽  
Powder Neutron Diffraction

The order–disorder phase transition in FeAl alloy for compositions 20.24, 24.15, 28.06. and 31.54 at.% Al has been studied by powder neutron diffraction. The phase transitions from α to FeAl and from FeAl to Fe3Al appear to be of a continuous nature. The value of the critical index β of the order parameter is found to be 0.302 ± 0.009.

scholarly journals MAJORITY-VOTE ON DIRECTED SMALL-WORLD NETWORKS

2007 ◽  
Vol 18 (08) ◽  
pp. 1251-1261 ◽  
Author(s):  
EDINA M. S. LUZ ◽  
F. W. S. LIMA
Keyword(s):  
Phase Transition ◽  
Monte Carlo ◽  
Critical Exponents ◽  
Order Parameter ◽  
Majority Vote ◽  
Small World ◽  
Small World Network ◽  
Small World Networks ◽  
Vote Model ◽  
Disorder Phase Transition

On directed small-world networks the majority-vote model with noise is now studied through Monte Carlo simulations. In this model, the order-disorder phase transition of the order parameter is well defined. We calculate the value of the critical noise parameter qc for several values of rewiring probability p of the directed small-world network. The critical exponents β/ν, γ/ν and 1/ν were calculated for several values of p.

scholarly journals MAJORITY-VOTE ON DIRECTED BARABÁSI–ALBERT NETWORKS

2006 ◽  
Vol 17 (09) ◽  
pp. 1257-1265 ◽  
Author(s):  
F. W. S. LIMA
Keyword(s):  
Phase Transition ◽  
Monte Carlo ◽  
Ising Model ◽  
Monte Carlo Simulations ◽  
Decay Time ◽  
Order Parameter ◽  
Majority Vote ◽  
Arrhenius Law ◽  
Vote Model ◽  
Disorder Phase Transition

On directed Barabási–Albert networks with two and seven neighbours selected by each added site, the Ising model was seen not to show a spontaneous magnetisation. Instead, the decay time for flipping of the magnetisation followed an Arrhenius law for Metropolis and Glauber algorithms, but for Wolff cluster flipping the magnetisation decayed exponentially with time. On these networks the Majority-vote model with noise is now studied through Monte Carlo simulations. However, in this model, the order-disorder phase transition of the order parameter is well defined in this system. We calculate the value of the critical noise parameter qc for several values of connectivity z of the directed Barabási–Albert network. The critical exponentes β/ν, γ/ν and 1/ν were calculated for several values of z.

scholarly journals INFLUENCE OF PRESSURE ON SMECTIC A-NEMATIC PHASE TRANSITION

1999 ◽  
Vol 13 (09n10) ◽  
pp. 275-283 ◽  
Author(s):  
KISOR MUKHOPADHYAY ◽  
PRABIR K. MUKHERJEE
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Phenomenological Model ◽  
Order Parameter ◽  
Nematic Phase ◽  
Tricritical Point ◽  
Second Order ◽  
Experimental Results ◽  
First Order ◽  
Smectic A

We propose a Landau-de Gennes phenomenological model to describe the pressure induced smectic A-nematic phase transition. The influence of pressure on smectic A-nematic phase transitions are discussed for varying coupling between orientational and translational order parameter with pressure. Increasing the pressure, the first order nematic-smectic A transition becomes second order at a tricritical point which agrees fairly well with available experimental results.

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