共查询到20条相似文献,搜索用时 15 毫秒
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This study explores the close-range, short-range and long-range relationships between the parameters of the Morse and Buckingham potential energy functions. The results show that the close-range and short-range relationships are valid for bond compression and for very small changes in bond length, respectively, while the long-range relationship is valid for bond stretching. A wide-range relationship is proposed to combine the comparative advantages of the close-range, short-range and long-range parameter relationships. The wide-range relationship is useful for replacing the close-range, short-range and long-range parameter relationships, thereby preventing the undesired effects of potential energy jumps resulting from functional switching between the close-range, short-range and long-range interaction energies. 相似文献
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The equivalent two-body method for a three-body system has been generalized to an arbitrary three-body system with short-range two-body interactions. An analytical expression for the long-range effective potential is obtained for the Gaussian potential, the Yukawa potential and the exponential potential. The asymptotic behavior of the effective potential at very large distance is found to be universal and an explanation on the significance of universality is given. The weakly bound excited state for the system is first obtained although there is no bound state for two-body subsystems. 相似文献
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Pierre-Henri Chavanis 《Physica A》2011,390(9):1546-1574
We develop the kinetic theory of Brownian particles with long- and short-range interactions. Since the particles are in contact with a thermal bath fixing the temperature T, they are described by the canonical ensemble. We consider both overdamped and inertial models. In the overdamped limit, the evolution of the spatial density is governed by the generalized mean field Smoluchowski equation including a mean field potential due to long-range interactions and a generically nonlinear barotropic pressure due to short-range interactions. This equation describes various physical systems such as self-gravitating Brownian particles (Smoluchowski-Poisson system), bacterial populations experiencing chemotaxis (Keller-Segel model) and colloidal particles with capillary interactions. We also take into account the inertia of the particles and derive corresponding kinetic and hydrodynamic equations generalizing the usual Kramers, Jeans, Euler and Cattaneo equations. For each model, we provide the corresponding form of free energy and establish the H-theorem and the virial theorem. Finally, we show that the same hydrodynamic equations are obtained in the context of nonlinear mean field Fokker-Planck equations associated with generalized thermodynamics. However, in that case, the nonlinear pressure is due to the bias in the transition probabilities from one state to the other leading to non-Boltzmannian distributions while in the former case the distribution is Boltzmannian but the nonlinear pressure arises from the two-body correlation function induced by the short-range potential of interaction. As a whole, our paper develops connections between the topics of long-range interactions, short-range interactions, nonlinear mean field Fokker-Planck equations and generalized thermodynamics. It also justifies from a kinetic theory based on microscopic processes, the basic equations that were introduced phenomenologically to describe self-gravitating Brownian particles, chemotaxis and colloidal suspensions with attractive interactions. 相似文献
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由原子在点阵中扩散的反应率过程理论,在最近邻近似下,计算了AB合金的长程有序化动力学及长程序为零时的短程有序化动力学。所得结果与前人的实验结论及计算结果相比定性地符合,定量地接近。长程有序化动力学的计算表明,有序化过程存在有孕育期,有c-曲线形式的转变曲线,s近似与exp{-αt2}正比,算得的平衡有序度与前人计算结果相近。长程序为零时的短程有序化动力学的计算表明,σ近似与exp{-βt}正比,此时有序化速率甚快,以致在最快的淬火速率下,样品中也必然存在有一定的短程序,所得的平衡短程序值也符合前人的计算结果。本文是作为继续计算短程有序化动力学的准备及基础。 相似文献
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A Monte Carlo simulation on the magnetic ordering of the artificial geometrically frustrated square lattice shows that the system exhibits the spin ice state and the disorder state for strong and weak dipolar interactions. We demonstrate that the long-range dipolar interactions are significant for the short-range spin ice state. 相似文献
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S. V. Starenchencko 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(2):203-208
The regularities of temperature-and strain-induced order-disorder phase transitions are determined from analyzing X-ray diffraction data. The results obtained are used to reveal common features in order-disorder transformations induced under energy actions of different types. It is established that, in both cases, the transition from the long-range order state to the short-range order state is accompanied by an increase in the number of defects in the structure of the alloy and the most rapid decrease in the long-range order parameter is associated with the generation of antiphase boundaries and their smearing. 相似文献
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We show existence and uniqueness for the solutions to the Newton equations relative to a system of infinitely many particles moving in the three-dimensional space and mutually interacting via a bounded superstable long-range potential. The present paper complete an analogous result obtained for positive short-range interaction. 相似文献
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We apply Kac's method of functional integration to a spatially non-uniform fluid with short and long-range interactions. The system with short-range interactions is treated as a reference system to which the long-range pair interaction is added as a perturbation. All equilibrium distribution functions of the reference system are assumed known. We show by diagram analysis that by a suitable choice of the density profile of the reference system the thermodynamic potential can be expressed in terms of a cluster expansion containing only irreducible diagrams. For a spatially uniform fluid in the thermodynamic limit our results reduce to those obtained by Siegert et al. 相似文献
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The evolution of the short-range structural signature of the Ir4+ dimer state in CuIr2S4 thiospinel has been studied across the metal-insulator phase transitions as the metallic state is induced by temperature, Cr doping, and x-ray fluence. An atomic pair distribution function (PDF) approach reveals that there are no local dimers that survive into the metallic phase when this is invoked by temperature and doping. The PDF shows Ir4+ dimers when they exist, regardless of whether or not they are long-range ordered. At 100 K, exposure to a 98 keV x-ray beam melts the long-range dimer order within a few seconds, though the local dimers remain intact. This shows that the metallic state accessed on warming and doping is qualitatively different from the state obtained under x-ray irradiation. 相似文献
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针对一种计算机网络模型,利用节点排队长度累计量的均方涨落函数,研究了网络节点在时间上的长程相关特性.结果表明,随着负载的增加,网络节点数据包排队长度在时间上由自由流状态的不相关或短程相关逐渐演变为临界和拥塞时的长程相关,关联范围逐渐增大,长程关联特性开始显现.在自由流状态时,节点的不相关或短程相关,并且有一致的数值为0.5的幂指数这一典型特征.而在临界状态时,节点数据包排队长度长程相关,有大于0.5的幂指数为特征.并且随网络规模的增大,节点间的群体作用逐渐显著,幂指数呈下降趋势.
关键词:
计算机网络
相变
长程相关
幂律 相似文献
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The K state can [1–7] have a marked effect on the mechanical parameters of homogeneous solid solutions containing transition elements. The K state is seen as a rise in resistance in low-temperature annealing after quenching from high temperatures and has been ascribed to the formation of short-range order [4, 5, 8–10] or of imperfect long-range order [6, 7]. The mechanical properties are also substantially affected. We have examined the effects on the dislocation starting stress as a function of temperature, as measured by mechanical hysteresis [18–20], in the K state range for Ni+17% Cr. 相似文献
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Argyriou DN Lynn JW Osborn R Campbell B Mitchell JF Ruett U Bordallo HN Wildes A Ling CD 《Physical review letters》2002,89(3):036401
Neutron scattering measurements on a bilayer manganite near optimal doping show that the short-range polaron correlations are completely dynamic at high T, but then freeze upon cooling to a temperature T(*) approximately equal 310 K. This glass transition suggests that the paramagnetic/insulating state arises from an inherent orbital frustration that inhibits the formation of a long-range orbital- and charge-ordered state. Upon further cooling into the ferromagnetic-metallic state (T(C) = 114 K), where the polarons melt, the diffuse scattering quickly develops into a propagating, transverse optic phonon. 相似文献
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We investigate the effect of geometry on the ground-state ordering of artificially frustrated magnetic rectangular and triangular lattices by Monte Carlo method. By varying the vertical lattice spacing while keeping the horizontal one fixed, we show that when the ratio of vertical to horizontal lattice spacing, labeled by η, is less than 1.82, the ground state of the rectangular lattice presents long-range antiferromagnetic order and for η?1.82 the ground state changes to long-range mixed ferromagnetic and antiferromagnetic order. For the frustrated triangular lattice, the short-range ordered state as well as two long-range ordered ground states occurs transiently at η=0.87 and 2, where the energies of the two ground states with long-range order are approximately equal. In addition, the level of frustration of both frustrated lattices is found to be largely relevant to the ratio η. 相似文献
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The quintessential two-dimensional lattice model that describes the competition between the kinetic energy of electrons and their short-range repulsive interactions is the repulsive Hubbard model. We study a time-reversal symmetric variant of the repulsive Hubbard model defined on a planar lattice: Whereas the interaction is unchanged, any fully occupied band supports a quantized spin Hall effect. We show that at 1/2 filling of this band, the ground state develops spontaneously and simultaneously Ising ferromagnetic long-range order and a quantized charge Hall effect when the interaction is sufficiently strong. We ponder on the possible practical applications, beyond metrology, that the quantized charge Hall effect might have if it could be realized at high temperatures and without external magnetic fields in strongly correlated materials. 相似文献
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We study the fluctuation-induced attraction of vortices for continuous anisotropic superconductors by using quantum statistical physics. In the low temperature or quantum limit, only the low-lying modes are relevant, the induced short-range attractive potential is proportional to (kBT)3K1(ΓR/λ), while in high temperature or classical limit, the induced attractive potential reduced to long-range van der Waals type kBT/R4 for two vortices separated by a distance R. 相似文献
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《Physics letters. A》2019,383(12):1235-1241
In this work, we analyze the q-state Potts model with long-range interactions through nonequilibrium scaling relations commonly used when studying short-range systems. We determine the critical temperature via an optimization method for short-time Monte Carlo simulations. The study takes into consideration two different boundary conditions and three different values of range parameters of the couplings. We also present estimates of some critical exponents, named as raw exponents for systems with long-range interactions, which confirm the non-universal character of the model. Finally, we provide some preliminary results addressing the relations between the raw exponents and the exponents obtained for systems with short-range interactions. The results assert that the methods employed in this work are suitable to study the considered model and can easily be adapted to other systems with long-range interactions. 相似文献