Hou Lu-Jing, Piel Alexander, Shukla P K
IEAP, Christian-Albrechts Universität zu Kiel, D-24098 Kiel, Germany.
Phys Rev Lett. 2009 Feb 27;102(8):085002. doi: 10.1103/PhysRevLett.102.085002. Epub 2009 Feb 25.
We perform Brownian dynamics simulations for studying the self-diffusion in two-dimensional (2D) dusty-plasma liquids, in terms of both mean-square displacement and the velocity autocorrelation function (VAF). Superdiffusion of charged dust particles has been observed to be the most significant at an infinitely small damping rate gamma for intermediate coupling strength, where the long-time asymptotic behavior of VAF is found to be the product of t;{-1} and exp(-gammat). The former represents the prediction of early theories in 2D simple liquids and the latter the VAF of a free Brownian particle. This leads to a smooth transition from superdiffusion to normal diffusion, and then to subdiffusion with an increase of the damping rate. These results well explain the seemingly contradictory observations scattered in recent classical molecular dynamics simulations and experiments of dusty plasmas.
我们通过均方位移和速度自相关函数（VAF），进行布朗动力学模拟，以研究二维（2D）尘埃等离子体液体中的自扩散。对于中等耦合强度，在无限小的阻尼率γ下，带电尘埃粒子的超扩散最为显著，此时VAF的长时间渐近行为被发现是t⁻¹与exp(-γt)的乘积。前者代表二维简单液体早期理论的预测，后者代表自由布朗粒子的VAF。这导致了从超扩散到正常扩散，然后随着阻尼率的增加到亚扩散的平滑转变。这些结果很好地解释了最近尘埃等离子体的经典分子动力学模拟和实验中分散的看似矛盾的观察结果。
