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Negative diffusion coefficient in a two-dimensional lattice-gas system with attractive nearest-neighbor interactions

机译:具有有吸引力的最近邻相互作用的二维晶格气系统中的负扩散系数

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摘要

Collective diffusion in a two-dimensional lattice-gas system undergoing first-order phase transition is studied both theoretically and by means of Monte Carlo (MC) simulations. The nearest-neighbor attractive interactions result in the formation of a two-phase mixture in which the characteristic size of the dense phase grows with time as t~(1/3). It is shown analytically that the evolution of large-scale coverage inhomogeneities is governed by the diffusion equation with a negative diffusion coefficient. Similar to the phenomenon of Ostwald ripening, the Gibbs-Thompson effect is responsible for this abnormal diffusion. MC simulations of random jumps of individual particles also show the presence of negative diffusion caused by the macroscopically inhomoge-neous distribution of particle density. The collective diffusion coefficients obtained both theoretically and by means of MC simulations are in satisfactory agreement.
机译:理论上和通过蒙特卡洛(MC)模拟研究了经历一阶相变的二维晶格气系统中的集体扩散。最近邻的吸引相互作用导致形成两相混合物,其中致密相的特征尺寸随时间t〜(1/3)增长。分析表明,大规模覆盖不均匀性的演化受扩散系数为负的扩散方程支配。与奥斯特瓦尔德熟化现象相似,吉布斯-汤普森效应是这种异常扩散的原因。单个粒子随机跳跃的MC模拟还显示,存在由粒子密度的宏观不均匀分布引起的负扩散。理论上和通过MC模拟获得的集体扩散系数都令人满意。

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