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arXiv 1104.3020cond-mat.stat-mechphysics.chem-ph
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格点自振子系统化学振荡的粗粒化模拟

Coarse-grained Simulations of Chemical Oscillation in a Lattice Brusselator System

Ting Rao, Zhen Zhang, Zhonghuai Hou, Houwen Xin

摘要:

加速粗粒化(CG)算法用于模拟表面系统上的非均相化学反应,最近得到了广泛的关注。在本文中,我们考虑这样一个问题,通过研究一个二维(2D)格子气自振子模型的振荡行为。我们采用了粗粒度的动力学蒙特卡罗(CG-KMC)程序,其中$m \times m$微观晶格位点被分组在一起,形成一个CG细胞,CG过程发生与定义良好的CG率。我们发现,然而,这样的CG方法几乎失败,如果CG率是由一个简单的局部平均场($s$ -LMF)近似获得,由于忽略了相邻细胞之间的相关性所造成的三分子反应在这个非线性系统。通过适当地纳入这样的边界效应,我们因此介绍了所谓的$b$ -LMF CG方法。大量的数值模拟表明,$b$ -LMF方法可以很好地再现系统的振荡行为,只要扩散常数不是太小。此外,我们发现,从KMC结果的偏差达到一个接近零的最低水平,在中间单元的大小,这是在有效扩散长度和维持一个明确的时间振荡所需的最小尺寸之间。

英文摘要:

Accelerated coarse-graining (CG) algorithms for simulating heterogeneous chemical reactions on surface systems have recently gained much attention. In the present paper, we consider such an issue by investigating the oscillation behavior of a two-dimension (2D) lattice-gas Brusselator model. We have adopted a coarse-grained Kinetic Monte Carlo (CG-KMC) procedure, where $m \times m$ microscopic lattice sites are grouped together to form a CG cell, upon which CG processes take place with well-defined CG rates. We find that, however, such a CG approach almost fails if the CG rates are obtained by a simple local mean field ($s$-LMF) approximation, due to the ignorance of correlation among adjcent cells resulted from the trimolecular reaction in this nonlinear system. By properly incorporating such boundary effects, we thus introduce the so-called $b$-LMF CG approach. Extensive numerical simulations demonstrate that the $b$-LMF method can reproduce the oscillation behavior of the system quite well, given that the diffusion constant is not too small. In addition, we find that the deviation from the KMC results reaches a nearly zero minimum level at an intermediate cell size, which lies in between the effective diffusion length and the minimal size required to sustain a well-defined temporal oscillation.

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