共查询到20条相似文献,搜索用时 15 毫秒
1.
The Mori formalism is used to study generalized transport coefficients in two dimensions. All finite multilinear products of the single particle density and momentum density comprise the set of the variables in the calculation of the self-diffusion coefficient. A self-consistent equation, which is a non-linear integral equation, is obtained for the leading asymptotic behavior of the generalized self-diffusion coefficient. An asymptotic solution is presented which for small wavevector (k) and frequency (s) behaves like , where D has the dimensions of a diffusion coefficient. The mean square and mean fourth displacements of a tagged particle are also calculated. The long time behavior of the momentum correlation function exhibits a tail of the form whose coefficient is dependent of the intermolecular potential. 相似文献
2.
The low density form of the generalized frequency (s) and wavevector (k) dependent self-diffusion coefficient D(k, s) is calculated, from which the low density forms of related quantities, e.g. the velocity autocorrelation function, are derived. Agreement is obtained with the low density kinetic theory results. A closed form expression for D(k, s) valid over a wide range of densities and times is also given, showing consistency between the asymptotic long time results, obtained previously, and the low density kinetic theory results. 相似文献
3.
V. V. Kabanov K. Zagar D. Mihailovic 《Journal of Experimental and Theoretical Physics》2005,100(4):715-721
The electric conductivity is calculated for regular inhomogeneous two-component isotropic medium in which droplets of one phase with conductivity σ2 are embedded in another, with conductivity σ1. An expression is formulated that can be used in many different situations and is of particular relevance in the case where the relative proportion of the components is temperature-dependent and varies over a wide range. Behavior of the effective conductivity depends on the spatial arrangements and the shape of the inclusions. 相似文献
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P. H. Chavanis 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(4):391-409
We derive the exact expression of the diffusion
coefficient of a self-gravitating Brownian gas in two
dimensions. Our formula generalizes the usual Einstein relation for
a free Brownian motion to the context of two-dimensional gravity. We
show the existence of a critical temperature Tc at which the
diffusion coefficient vanishes. For T < Tc, the diffusion
coefficient is negative and the gas undergoes gravitational
collapse. This leads to the formation of a Dirac peak concentrating
the whole mass in a finite time. We also stress that the critical
temperature Tc is different from the collapse temperature
T* at which the partition function diverges. These quantities
differ by a factor 1-1/N where N is the number of particles in
the system. We provide clear evidence of this difference by
explicitly solving the case N = 2. We also mention the analogy with
the chemotactic aggregation of bacteria in biology, the formation
of “atoms” in a two-dimensional (2D) plasma and the formation of
dipoles or “supervortices” in 2D point vortex dynamics. 相似文献
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7.
A. Gold 《Zeitschrift für Physik B Condensed Matter》1991,83(3):429-440
Analytical results for the frequency-dependent conductivity of a disordered two-dimensional interacting Bose condensate are presented. Charged and uncharged impurities are considered. We find that for weak disorder the condensate is a superfluid while for strong disorder it is an insulator (a Bose glass). At the superfluid-insulator transition point (at the critical boson densityN
c) the condensate exhibits metallic tranport properties. An loffe-Regel criterion for the transition point is derived. The conductivity at the transition point is of ordere
2/h (h is Planck's constant) and depends on the kind of disorder. For charged impurities (with impurity densityN
i) the conductivity (for a condensate of particles with charge 2e and forN
i=2N
c) at the transition point is given by
c
=0.26x(2e)2/h. We discuss recent experiments on superconducting ultra-thin films and on high-T
c superconductors. 相似文献
8.
A. A. Selezenev A. Yu. Aleinikov P. V. Ermakov N. S. Ganchuk S. N. Ganchuk R. E. Jones 《Physics of the Solid State》2012,54(3):462-467
The thermal conductivity coefficient of the germanium crystal lattice has been calculated by molecular dynamics simulation.
Calculations have been performed for both the perfect crystal lattice and the crystal lattice with defects such as monovacancies.
For the perfect germanium single crystal, the dependence of the thermal conductivity coefficient on the lattice temperature
has been obtained in the temperature range of 150–1000 K. The thermal conductivity coefficient of the germanium lattice has
been calculated as a function of the monovacancy concentration. 相似文献
9.
James Glimm 《Communications in Mathematical Physics》1967,6(1):61-76
The Yukawa coupling in two dimensional space time is considered. A space outoff is introduced in the interaction termV, so that the renormalized HamiltonianH
ren is a rigorously defined bilinear form in the Fock Hilbert space. The main result is thatH
ren is positive provided the finite part of the renormalization terms are suitably chosen. As a consequence, the Schrödinger equation (i/t–H
ren)=0 can be solved.This work was supported in part by the National Science Foundation, GP — 6165. 相似文献
10.
A review and some new results are presented for the solid-on-solid models of wetting in two dimensions (i.e., line interfaces) with an emphasis on the difference equations arising in the transfer matrix calculations for these models. Methods for solving the appropriate difference equations exactly or approximately are surveyed, including specific results for short-range, long-range power-law, and applied field-like (binding) external potentials. 相似文献
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B.M. Zawilski R.T. Littleton IV N.D. Lowhorn T.M. Tritt 《Solid State Communications》2010,150(29-30):1299-1302
The recent theoretical one-dimensional models display invariably anomalous thermal conductivity. Thermal conductivity of several low-dimensional crystalline systems has been investigated using our new techniques. The results show that for most of the measured materials in the high temperature range the thermal conductivity is composed of two extremes: a low- and a high-conductive state. The effective thermal conductivity jumps abruptly between these two states giving rise to apparent discontinuities or “spikes”. 相似文献
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The lattice thermal conductivity of three II–VI compounds, ZnS, ZnSe, and ZnTe has been analysed on the basis of full Callaway's formalism by considering the scattering of phonons by boundary, point defects, normal, and Umklapp processes. An acceptable agreement with the experimental results is found up to 250 K. From the analysis of the adjustable parameters useful information about the lattice anharmonicity and defects have been obtained. 相似文献
16.
A. V. Yeganyan A. S. Kuzanyan V. Stathopoulos 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2014,49(4):176-179
A generalized expression for approximate estimation of lattice component of thermal conductivity coefficient for solid-state crystal dielectrics at temperatures higher than the Debye temperature, is obtained, which is convenient for preliminary estimation of thermal conductivity coefficient and enables one to conduct a goal-directed search for low-conductivity materials. On the example of rare-earth magnesium hexaaluminates, it is shown that estimations according to the obtained expression are in good compliance with experimental data. 相似文献
17.
A. V. Yeganyan T. I. Butaeva E. P. Kokanyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2017,52(4):387-391
At high temperatures, the simple expression for thermal conductivity of crystals with the garnet structure is obtained, which allows one to determine this quantity if the lattice constant or density of these crystals is known. The thermal conductivity coefficients for the garnet crystals of different compositions calculated from the obtained formula are in a good agreement with the experimentally measured values. 相似文献
18.
A. A. Selezenev A. Yu. Aleinikov N. S. Ganchuk S. N. Ganchuk R. E. Jones J. A. Zimmerman 《Physics of the Solid State》2013,55(4):889-894
The thermal conductivity coefficients of single-layer and multilayer graphene sheets have been calculated using the molecular dynamics simulation. Calculations have been performed for graphene sheets with lengths in the range 20–130 nm and at average temperatures in the range 230–630 K. The results obtained have been compared with the experimental data and results of calculations carried out in other works. 相似文献
19.