共查询到20条相似文献,搜索用时 31 毫秒
1.
《Physics letters. A》2020,384(4):126100
In this paper, we consider the interaction of small amplitude waves (phonons) with standing discrete breather (DB) in the one-dimensional chain of harmonically coupled particles interacting with the anharmonic one-site potential, which can be of hard-type or soft-type anharmonicity. The coefficients of phonon reflection and transmission are calculated numerically. It is found that for the case of hard-type anharmonicity (soft-type anharmonicity) DBs are more transparent for short-wavelength (long-wavelength) phonon waves, while they efficiently reflect long-wavelength (short-wavelength) phonons. In thermal equilibrium, when all phonons have equal energy density, it is found that for the same width of the transparency window, DB transmits less energy in the case of the hard-type anharmonicity. This is so because, in this case, DB reflects long-wavelength phonons, which have larger group velocity and hence greater contribution to the net energy flux through the DB. In this sense, DBs more efficiently suppress thermal conductivity in the chain with hard-type anharmonicity. Our results contribute to a better understanding of the role of discrete breathers in the heat flow in nonlinear chains. 相似文献
2.
A. Akbari Tochaei H. Arabshahi M. R. Benam A. Vatan-Khahan M. Abedininia 《Journal of Experimental and Theoretical Physics》2016,122(5):869-873
The discrete breathers in graphane in thermodynamic equilibrium in the temperature range 50–600 K are studied by molecular dynamics simulation. A discrete breather is a hydrogen atom vibrating along the normal to a sheet of graphane at a high amplitude. As was found earlier, the lifetime of a discrete breather at zero temperature corresponds to several tens of thousands of vibrations. The effect of temperature on the decay time of discrete breathers and the probability of their detachment from a sheet of graphane are studied in this work. It is shown that closely spaced breathers can exchange energy with each other at zero temperature. The data obtained suggest that thermally activated discrete breathers can be involved in the dehydrogenation of graphane, which is important for hydrogen energetics. 相似文献
3.
K.Ø. Rasmussen S. Aubry A.R. Bishop G.P. Tsironis 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):169-175
We study the dynamics of the discrete nonlinear Schr?dinger lattice initialized such that a very long transitory period of
time in which standard Boltzmann statistics is insufficient is reached. Our study of the nonlinear system locked in this non-Gibbsian state focuses on the dynamics of discrete breathers (also called intrinsic localized modes). It is found that part of the
energy spontaneously condenses into several discrete breathers. Although these discrete breathers are extremely long lived,
their total number is found to decrease as the evolution progresses. Even though the total number of discrete breathers decreases
we report the surprising observation that the energy content in the discrete breather population increases. We interpret these
observations in the perspective of discrete breather creation and annihilation and find that the death of a discrete breather
cause effective energy transfer to a spatially nearby discrete breather. It is found that the concepts of a multi-frequency
discrete breather and of internal modes is crucial for this process. Finally, we find that the existence of a discrete breather
tends to soften the lattice in its immediate neighborhood, resulting in high amplitude thermal fluctuation close to an existing
discrete breather. This in turn nucleates discrete breather creation close to a already existing discrete breather.
Received 21 January 1999 and Received in final form 20 September 1999 相似文献
4.
The density of phonon states at various temperatures has been calculated for crystals with the NaCl structure with equal and strongly differing weights of anions and cations. It has been shown that, in the crystal with a considerable difference in the weights of components, a wide band gap exists in the spectrum of phonon states, which leads to spontaneous excitation of nonlinear localized vibrational modes??gap discrete breathers having frequencies inside the band gap, if the temperature is sufficiently high. It has been found that the peak of the density of phonon states lying above the spectrum of linear vibrations appears at elevated temperatures, which can indicate the existence of discrete breathers with corresponding frequencies. It has been noted that, previously, the existence of gap discrete breathers in the NaI crystal at 555 K was shown experimentally. The presented results bring up the question of the theoretical justification and experimental observation of the breathers with frequencies above the phonon spectrum. 相似文献
5.
G.H. Zhou Q.L. Xia J.R. Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):207-213
Moving nonlinear localized vibrational modes (i.e. discrete breathers) for the one-dimensional homogenous lattice with quartic anharmonicity are obtained analytically by means
of a semidiscrete approximation plus an integration. In addition to the pulse-envelope type of moving modes which have been
found previously both analytically and numerically, we find that a kink-envelope type of moving mode which has not been reported
before can also exist for such a lattice system. The two types of modes in both right- and left-moving form can occur with
different carrier wavevectors and frequencies in separate parts of the plane. Numerical simulations are performed and their results are in good agreement with the analytical predictions.
Received 13 October 1999 and Received in final form 15 May 2000 相似文献
6.
It has been shown recently that a moving discrete breathers localized in one close-packed atomic row can be excited in a two-dimensional monoatomic crystal with Morse interaction. In this work, a motionless discrete breathers having the threefold symmetry axis has been excited in the same crystal. The initial conditions for the excitation of such discrete breathers are set by the superposition of a bell-shaped function on a planar nonlinear phonon mode with the wave vector lying at the edge of the Brillouin zone. In addition, the displacement of the centers of atomic oscillations from the center of the discrete breathers owing to the asymmetry of the Morse potential is taken into account. The results obtained make it possible to approach the search for highly symmetric discrete breathers in three-dimensional crystals. 相似文献
7.
Tsironis GP 《Chaos (Woodbury, N.Y.)》2003,13(2):657-666
Intense work on discrete breathers or intrinsic localized modes in recent years has revealed a wealth of new properties of classical energy localization. Relaxation and mobility in particular may be two of the critical links with biomolecular processes. We review some of the basic discrete breather properties that we think are pertinent to biomolecules and make conjectures as to their possible biological utility. 相似文献
8.
The discrete gap breathers (DGBs) in a one-dimensional diatomic chain with K2-K3-K4 potential are analysed. Using the local anharmonicity approximation, the analytical investigation has been implemented. The dependence of the central amplitude of the discrete gap breathers on the breather frequency and the localization parameter are calculated. With increasing breather frequency, the DGB amplitudes decrease. As a function of the localization parameter, the central amplitude exhibits bistability, corresponding to the two branches of the curve ω = ω(ζ). With a nonzero cubic term, the HS mode of DGB profiles becomes weaker. With increasing K3, the HS mode of DGB profiles becomes weaker and a bit narrower. For the LS mode, with increasing K3, the central particle amplitude becomes larger, and the DGB profile becomes much sharper. But, as k3 increases further, the central particle amplitude of the LS mode becomes smaller. 相似文献
9.
Compact-like discrete breather and its stability in a discrete monatomic Klein--Gordon chain 下载免费PDF全文
This paper studies a discrete one-dimensional monatomic
Klein--Gordon chain with only quartic nearest-neighbor interactions,
in which the compact-like discrete breathers can be explicitly
constructed by an exact separation of their time and space
dependence. Introducing the trying method, it proves that
compact-like discrete breathers exist in this nonlinear system. It
also discusses the linear stability of the compact-like discrete
breathers, when the coefficient (β) of quartic on-site
potential and the coupling constant (K4) of quartic interactive
potential satisfy the given conditions, they are linearly stable. 相似文献
10.
Existences and stabilities of bright and dark breathers in a general one-dimensional discrete monatomic Chain 下载免费PDF全文
A general one-dimensional discrete monatomic model is investigated
by using the multiple-method. It is proven that the discrete bright
breathers (DBBs) and discrete dark breathers (DDBs) exist in this
model at the anti-continuous limit, and then the concrete models of
the DBBs and DDBs are also presented by the multiple-scale approach
(MSA) and the quasi-discreteness approach (QDA). When the results
are applied to some particular models, the same conclusions as those
presented in corresponding references are achieved. In addition, we
use the method of the linearization analysis to investigate this
system without the high order terms of $\varepsilon$. It is found
that the DBBs and DDBs are linearly stable only when coupling
parameter $\chi$ is small, of which the limited value is obtained by
using an analytical method. 相似文献
11.
Murzaev R. T. Semenov A. S. Potekaev A. I. Starostenkov M. D. Zakharov P. V. Kulagina V. V. Dmitriev S. V. 《Russian Physics Journal》2021,64(2):293-301
Russian Physics Journal - An analysis of spatially localized and time-periodic vibrational modes (discrete breathers – DBs) is carried out. It is found out that the discreteness and... 相似文献
12.
In this paper we study the existence and stability of two-dimensional discrete gap
breathers in a two-dimensional diatomic face-centered square lattice
consisting of alternating light and heavy atoms, with on-site
potential and coupling potential. This study is focused on
two-dimensional breathers with their frequency in the gap that
separates the acoustic and optical bands of the phonon spectrum. We
demonstrate the possibility of the existence of two-dimensional gap
breathers by using a numerical method. Six types of two-dimensional
gap breathers are obtained, i.e., symmetric, mirror-symmetric and
asymmetric, whether the center of the breather is on a light or a
heavy atom. The difference between one-dimensional discrete gap
breathers and two-dimensional discrete gap breathers is also
discussed. We use Aubry's theory to analyze the stability of
discrete gap breathers in the two-dimensional diatomic face-centered
square lattice. 相似文献
13.
It is shown how the self-consistent phonon Ansatz leads to a new class of exactly soluble models of a structural phase transition. Both nonpolynomial anharmonicity and disorder are analyzed in detail. In the classical limit, the thermodynamics is obtained and sufficient conditions on the anharmonicity are given to ensure a soft-mode phase transition. Diagonal disorder has been studied numerically. It is found that in three dimensions a pronounced mobility edge, separating localized and delocalized phonon states, may exist. 相似文献
14.
The Peyrard-Bishop model, which describes the dynamics of a DNA molecule, is considered. The solutions that represent discrete breathers are derived in the framework of the model. The dynamic stability of the stationary discrete breathers with respect to small perturbations is studied. The solutions can be interpreted as the experimentally observed opening of the base pairs in the DNA double strand at the initial stages of denaturation. It is also demonstrated that the model allows the existence of mobile breathers that move in the absence of perturbations in the environment. The interaction of the mobile breathers is numerically simulated. The Peierls-Nabarro barrier and the effective mass and velocity of the breather are estimated. 相似文献
15.
Appreciable elastic strain may considerably change the physical properties of crystals. This effect underlies the elastic
stress technology, which has been intensively developed in recent years. The influence of elastic strain on the density of
phonon states and on the properties of discrete breathers in the gap of the phonon spectrum of a crystal with a NaCl structure
and a considerable difference between the anion and cation masses is studied using the molecular dynamics method. A number
of crystal straining modes are considered. It is shown that the shear components of the strain tensor may significantly change
the density of phonon states but slightly influence the frequencies of discrete breathers. Compression (tensile) strains raise
(lower) the frequency of discrete breathers with a respective polarization. 相似文献
16.
Nonlinear classical Hamiltonian lattices exhibit generic solutions — discrete breathers. They are time-periodic and (typically exponentially) localized in space. The lattices have discrete translational symmetry. Discrete breathers are not confined to certain lattice dimensions. We will introduce the concept of these localized excitations and review their basic properties including dynamical and structural stability. We then focus on advances in the theory of discrete breathers in three directions — scattering of waves by these excitations, persistence of discrete breathers in long transient processes and thermal equilibrium, and their quantization. The second part of this review is devoted to a detailed discussion of recent experimental observations and studies of discrete breathers, including theoretical modelling of these experimental situations on the basis of the general theory of discrete breathers. In particular we will focus on their detection in Josephson junction networks, arrays of coupled nonlinear optical waveguides, Bose–Einstein condensates loaded on optical lattices, antiferromagnetic layered structures, PtCl based single crystals and driven micromechanical cantilever arrays. 相似文献
17.
A. Maluckov Lj. Hadžievski M. Stepić 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(3):333-341
Symmetric collisions of two discrete breathers in the
lattice with saturable nonlinearity are investigated. The strong
correlation of the collision properties and the parameters of
colliding breathers (power, velocity, and phase difference),
lattice parameters and position of the collision point is found.
This is related to the internal structure of the colliding
breathers and energy exchange with the phonon background. The type
of collision changes from elastic to the inelastic (the breathers
merging, multi-bounce interactions, breather creation etc.) with
the increasing of the colliding breather power. Collision of high
power breathers always results in the breather fusion. The elastic
and inelastic collisions are related to the periodic and
quasi-periodic colliding breathers, respectively. 相似文献
18.
《Physics Reports》1998,295(5):181-264
Nonlinear classical Hamiltonian lattices exhibit generic solutions in the form of discrete breathers. These solutions are time-periodic and (typically exponentially) localized in space. The lattices exhibit discrete translational symmetry. Discrete breathers are not confined to certain lattice dimensions. Necessary ingredients for their occurrence are the existence of upper bounds on the phonon spectrum (of small fluctuations around the groundstate) of the system as well as the nonlinearity in the differential equations. We will present existence proofs, formulate necessary existence conditions, and discuss structural stability of discrete breathers. The following results will be also discussed: the creation of breathers through tangent bifurcation of band edge plane waves; dynamical stability; details of the spatial decay; numerical methods of obtaining breathers; interaction of breathers with phonons and electrons; movability; influence of the lattice dimension on discrete breather properties; quantum lattices — quantum breathers.Finally we will formulate a new conceptual approach capable of predicting whether discrete breathers exist for a given system or not, without actually solving for the breather. We discuss potential applications in lattice dynamics of solids (especially molecular crystals), selective bond excitations in large molecules, dynamical properties of coupled arrays of Josephson junctions, and localization of electromagnetic waves in photonic crystals with nonlinear response. 相似文献
19.
Graphane is a fully hydrogenated graphene which is practically interesting for application in electronics, hydrogen storage and transportation, in nanoscale devices. As it was previously shown, the energy of a discrete breather (nonlinear localized mode) in graphane close to the value of the energy barrier at which the dehydrogenation of graphene occurs. In the present work, molecular dynamics simulation is used to investigate the possibility of energy exchange between discrete breathers in graphane in thermal equilibrium at 400 K and 600 K. In thermally equilibrated graphane, hydrogen atoms are spontaneously excited and can be considered as discrete breathers. Comparison of the kinetic energy per atom as the function of time for the selected hydrogen atoms with their displacements along the z axis showed that there is an energy exchange between the discrete breathers at evaluated temperatures. Hydrogen atom, transmitting its energy to the neighboring atom no longer exists as discrete breather. At high temperatures (600 K) the energy exchange between closely located discrete breathers also take place but strong thermo-oscillations of atoms at high temperatures (above 400 K) considerably affect the process. 相似文献
20.
Breathers in discrete nonlinear ferrimagnetic spin lattices are investigated for both easy-axis and easy-plane configurations.
The region in frequency space of the formation of breathers is determined and the anticontinuum limit discussed. The monochromatic
and the coloured breathers are found out numerically for different parameters and different conditions of excitations. 相似文献