Difference of Directions Between External Driving Force and Movement Direction of Center of Mass

Driven dynamics of a two-dimensional Frenkel-Kontorova model is studied in the paper. In our numerical simulations, it is found that the movement direction of the center of mass is not consistent with that of the external driving force except for some special symmetric directions at the lower driving force. Our results also indicate that the movement direction of the center of mass strongly depends on both the magnitude and the direction of the external driving force as well as the misfit angle between two layers.     

Peculiarities of dislocation motion in aluminum with allowance for the Peierls relief in the presence of ultrasound

Physics of the Solid State - The effect of ultrasound on motion of the Frenkel–Kontorova dislocations in aluminum has been studied with inclusion of the Peierls relief. A dislocation moves at...     

Newton trajectories for the tilted Frenkel–Kontorova model

ABSTRACT

Newton trajectories are used for the Frenkel–Kontorova model of a finite chain with free-end boundary conditions. We optimise stationary structures, as well as barrier breakdown points for a critical tilting force were depinning of the chain happens. These special points can be obtained straight forwardly by the tool of Newton trajectories. We explain the theory and add examples for a finite-length chain of a fixed number of 2,?3,?4,?5 and 23 particles.     

Properties of solitons in the Frenkel-Kontorova model

An exact numerical calculation is presented for the properties of solitons in the discrete model of Frenkel and Kontorova. We have calculated the single soliton energy, the Peierls pinning energy and the soliton-soliton interaction energy. The exponential behaviour predicted for the soliton-soliton interaction by the continuum approximation is found to hold even for large soliton densities and very strong substrate potentials though in the latter case, the coefficients differ substantially from those of the continuum approximation.     

Destruction of classical cantori in the quantum Frenkel-Kontorova model

In this paper we investigate the properties of the quantized discrete Frenkel Kontorova model. The structure of the ground state is numerically analyzed by means of the Metropolis algorithm; special attention is given to the effects of quantization on the Cantori structure of the classical ground state. These quantum effects produce a new structure which can be approximately described by using a sawtooth map instead of the Standard map. The dependence of the quantum energy on temperature is also investigated and discussed in connection with these structural modifications.     

Diffusion of interacting Brownian particles on non-regularly spaced stepped structures

In this paper, we investigate the diffusion process of interacting Brownian particles on stepped surfaces through a Langevin dynamic simulation method. Our primary interest is the investigation of the dynamics properties by calculating the collective diffusion coefficient for non-regularly spaced stepped structures using the Frenkel–Kontorova repulsive interactions. In particular, we have studied the effects of the Ehrlich–Schwoebel barrier $E_{S}$ and the additional binding energy $E_{B}$ on the diffusion process. Overall, our simulation results show that the value of the diffusion coefficient $D$ is reduced with increasing $E_{S}$ and $E_{B}$ . This reduction is also observed when decreasing the size of terraces. This diminution is well interpreted by calculating the effective potential which includes the effect of both potentials of Frenkel–Kontorova and the substrate.     

The ground state of the Frenkel–Kontorova model

The continual approximation of the ground state of the discrete Frenkel–Kontorova model is tested using a symmetric algorithm of numerical simulation. A “kaleidoscope effect” is found, which means that the curves representing the dependences of the relative extension of an N-atom chain vary periodically with increasing N. Stairs of structural transitions for N ? 1 are analyzed by the channel selection method with the approximation N = ∞. Images of commensurable and incommensurable structures are constructed. The commensurable–incommensurable phase transitions are stepwise.     

Buckling induced by a topological defect in a chain

The chain buckling induced by a topological defect (anti-kink) is investigated using a generalized Frenkel–Kontorova model. Instead of a single-peak appeared in the classical Euler instability, the buckling shape induced by the topological defect is a Sine-like pattern (two-peaks) that is antisymmetric regarding the point of the maximum stress. Evolution of the unstable buckling mode is clearly characterized by two time scales: one is the lifetime of the unstable phase, the other is the growth rate of the new phase. The phase transition curve of the buckling is a linear function of the chain length.     

Numerical Simulation of the Movement of Frenkel–Kontorova Dislocations in Aluminum Single Crystals at Low Temperatures

The motion of Frenkel–Kontorova dislocations in the single crystals of aluminum at low temperatures has been studied, by means of the computer simulation. It is shown that the dislocation movement is realized by the quantum tunneling of the kinks of dislocations through the Peierls barriers. It is shown that the action of the Peierls high barrier is analogous to the action of low temperatures, and if the Peierls barrier overcome, the dislocation moves unevenly, accelerating under the action of the Peierls barrier and slowing down after overcoming the Peierls barrier. Based on the numerical experiment, the mean free path of dislocation, the distance between the Peierls potential barriers and the width of the Peierls barrier are calculated. The computed values correspond to the real values.     

不公度相及公度-不公度相变:一维情形

本文通过Ｆｒｅｎｋｅｌ Ｋｏｎｔｏｒｏｖａ（ＦＫ）模型评述了凝聚态物理中的一个重要课题：不公度相和公度 不公度（ＣＩ）相变。论述主要集中在一维情形,对不公度相和ＣＩ相变的概念、物理图象、产生机制、研究背景、研究目标和意义进行了必要的介绍;概述了早期、近期和现代研究过程中一些典型的基本理论和方法;对标准ＦＫ模型及原子间势为凸函数的ＦＫ模型、经典非凸ＦＫ模型、ＦＫ模型的量子效应、一维双原子链ＦＫ模型、ＦＫ模型向二维和三维的推广、ＣＩ相变的有限温度效应等专题的研究进展作了概述,并指出了一些有待进一步探讨的课题。     

Interface-facilitated energy transport in coupled Frenkel–Kontorova chains

The role of interface couplings on the energy transport of two coupled Frenkel–Kontorova (FK) chains is explored through numerical simulations. In general, it is expected that the interface couplings result in the suppression of heat conduction through the coupled system due to the additional interface phonon–phonon scattering. In the present paper, it is found that the thermal conductivity increases with increasing intensity of interface interactions for weak inter-chain couplings, whereas the heat conduction is suppressed by the interface interaction in the case of strong inter-chain couplings. Based on the phonon spectral energy density method, we demonstrate that the enhancement of energy transport results from the excited phonon modes (in addition to the intrinsic phonon modes), while the strong interface phonon–phonon scattering results in the suppressed energy transport.     

Directed transport of modulated structures in the Frenkel–Kontorova model with a pulsating coupling

We study the directed transport of commensurate and incommensurate modulated phases of the Frenkel–Kontorova model by (parametric driving) periodic pulsed variation of the nearest-neighbor coupling in the dissipative limit of the dynamics. We obtain that a directed current flow appears as the amplitude of the pulsating coupling C increases above a threshold coupling C_th. This threshold coupling depends on the average interspacing ω between the oscillators displaying singularities as the system becomes commensurable with the underlying lattice. By making use of the discommensuration theory of modulated phases we obtain that the dependence of the directed current on ω is a piecewise linear function with integer slope. Numerical results confirm these predictions.     

不公度相及公度—不公度相变：一维情形

本文通过ＦｒｅｎｋｅｌＫｏｎｔｏｒｏｖａ（ＦＫ）模型评述了凝聚态物理中的一个重要课题：不公度相和公度不公度（ＣＩ）相变。论述主要集中在一维情形,对不公度相和ＣＩ相变的概念、物理图象、产生机制、研究背景、研究目标和意义进行了必要的介绍;概述了早期、近期和现代研究过程中一些典型的基本理论和方法;对标准ＦＫ模型及原子间势为凸函数的ＦＫ模型、经典非凸ＦＫ模型、ＦＫ模型的量子效应、一维双原子链ＦＫ模型、ＦＫ模型向二维和三维的推广、ＣＩ相变的有限温度效应等专题的研究进展作了概述,并指出了一些有待进一步探讨的课题。     

PAC-study of defects in n-type germanium

Using perturbed angular correlations of γ rays the behaviour of Frenkel defects in n-type germanium is studied.¹¹¹In/¹¹¹Cd probes either serve as primary knock-on atoms in the production of Frenkel defects by neutrino recoil or as trapping agents for defects produced by electron irradiation. The neutrino recoil process leads to a defect which is characterized by vQ=e²qQ/h=42(2) MHz (η=0.6), while a defect with vQ=423(1) MHz (η=0) is observed after electron irradiation and thermal annealing.     

First-Principles Calculations of Atomic and Electronic Properties of T1 and In on Si（111）

The atomic and electronic structures of T1 and In on Si（111） surfaces are investigated using the firstprinciples total energy calculations. Total energy optimizations show that the energetically favored structure is 1/3 ML T1 adsorbed at the T4 sites on Si（111） surfaces. The adsorption energy difference of one T1 adatom between （√3 × √3） and （1 × 1） is less than that of each In adatom. The DOS indicates that TI 6p and Si 3p electrons play a very important role in the formation of the surface states. It is concluded that the bonding of TI adatoms on Si（111） surfaces is mainly polar covalent, which is weaker than that of In on Si（111）. So T1 atom is more easy to be migrated than In atom in the same external electric field and the structures of T1 on Si（111） is prone to switch between （√3 × √3） and （1 × 1）.     

Study on the pre-chopper in CSNS LEBT

Physical designing of the pre-chopper in CSNS LEBT is carried out, which includes the deflecting voltage, the length and the width of the deflecting plates, and the gap between the deflecting plates. The most outstanding feature of the design is that both the gap and the width vary with the beam envelope size. So both the requried deflecting voltage and the loaded capacitance are lowered. In order to avoid destruction of the space charge neutralization by the pre-chopper in the whole LEBT, an electron-trapping electrode is arranged to confine the electrostatic field of the pre-chopper to the local area. To examine the reliability of the pre-chopping design in CSNS LEBT, a similar pre-chopping design in ADS RFQ LEBT is set up and an experiment on the pre-chopper is prepared. 3-dimensional simulations are carried out to determine the loaded capacitance and the applied voltage of the electron-trapping electrode.     

Synchronization in a Mutualism Ecosystem Induced by Noise Correlation

Understanding the cause of the synchronization of population evolution is an important issue for ecological improvement. Here we present a Lotka-Volterra-type model driven by two correlated environmental noises and show, via theoretical analysis and direct simulation, that noise correlation can induce a synchronization of the mutualists. The time series of mutual species exhibit a chaotic-like fluctuation, which is independent of the noise correlation, however, the chaotic fluctuation of mutual species ratio decreases with the noise correlation. A quantitative parameter defined for characterizing chaotic fluctuation provides a good approach to measure when the complete synchronization happens.     

Metric of States

Metric of quantum states plays an important role in quantum information theory. In this letter, we find the deep connection between quantum logic theory and quantum information theory. Using the method of quantum logic, we can get a famous inequality in quantum information theory, and we answer a question raised by S. Gudder.     

Remarks on interpretations of the Eotvos experiment and misinterpretation of E=mc^2

The Eotvos experiment on the verification of equivalence between inertial mass and gravitational mass of a body is famous for its accuracy. A question is, however, can these experimental results be applied to the case of a physical space in general relativity, where the space coordinates could be arbitrary？ It is pointed out that it can be validly applied because it has been proven that Einstein＇s equivalence principle for a physical space must have a frame of reference with the Euclidean-like structure. Will claimed further that such an overall accuracy can be translated into an accuracy of the equivalence between inertial mass and each type of energy. It is shown that, according to general relativity, such a claim is incorrect. The root of this problem is due to an inadequate understanding of special relativity that produced the famous equation E=mc^2, which must be understood in terms of energy conservation. Concurrently, it is pointed out that this error is a problem in Will＇s book, ‘Theory and Experiment in Gravitational Physics＇.