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arXiv 1010.4540cond-mat.softcond-mat.stat-mech
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准一维通道中相互作用粒子从单列扩散到二维扩散的转变

Transition from single-file to two-dimensional diffusion of interacting particles in a quasi-one-dimensional channel

D. Lucena, D. V. Tkachenko, K. Nelissen, V. R. Misko, W. P. Ferreira, G. A. Farias, F. M. Peeters

摘要:

采用分子动力学(MD)模拟方法研究了相互作用粒子在\textit{quasi} -一维(Q1 D)通道中的扩散特性.我们数值计算了均方位移(MSD),并研究了通道宽度(或限制势强度)对不同形状(即,直的和圆形的)。从单行扩散(SFD)的二维扩散制度的过渡进行了研究。这种转变(关于MSD $<Δx^{2}(t)>$ $\propto t^α$的标度指数($α$)的计算)作为通道宽度的函数,示出根据通道的限制轮廓而改变。特别地,过渡可以是平滑的(即,对于抛物线限制势)或相当尖锐/阶梯式(即,对于硬壁势),这与其中该过渡是突然的无限通道不同。这一结果可以用不同约束势下粒子密度的不同分布来解释。

英文摘要:

Diffusive properties of a monodisperse system of interacting particles confined to a \textit{quasi}-one-dimensional (Q1D) channel are studied using molecular dynamics (MD) simulations. We calculate numerically the mean-squared displacement (MSD) and investigate the influence of the width of the channel (or the strength of the confinement potential) on diffusion in finite-size channels of different shapes (i.e., straight and circular). The transition from single-file diffusion (SFD) to the two-dimensional diffusion regime is investigated. This transition (regarding the calculation of the scaling exponent ($α$) of the MSD $<Δx^{2}(t)>$ $\propto t^α$) as a function of the width of the channel, is shown to change depending on the channel's confinement profile. In particular the transition can be either smooth (i.e., for a parabolic confinement potential) or rather sharp/stepwise (i.e., for a hard-wall potential), as distinct from infinite channels where this transition is abrupt. This result can be explained by qualitatively different distributions of the particle density for the different confinement potentials.

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