Does Shape Anisotropy Control the Fractal Dimension in Diffusion-Limited Cluster-Cluster Aggregation?
Does Shape Anisotropy Control the Fractal Dimension in Diffusion-Limited Cluster-Cluster Aggregation?
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DOI：
10.1080/02786826.2010.516032
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发表时间：
2010-01-01
影响因子：
5.2
通讯作者：
Chakrabarti, A.
中科院分区：
文献类型：
--
作者：
Heinson, W. R.;Sorensen, C. M.;Chakrabarti, A.
受最近关于预混火焰中碳烟形成的实验的启发，我们在模拟研究中解决了同样的问题：在给定的聚集体中是否存在分维的分布，以及团簇的形状各向异性是否控制了分维？然而，我们的结果清楚地表明，经典的DLCA产生了各种形状的聚集体，D-f接近于1.8，与它们的形状无关，但在旋转半径R-g、质量N、单体半径a和分维D-f之间的关系中，具有形状相关的前因子k(0)，N=k(0)(Rg/a)(Df)。因此，预因数k(0)获得了作为集合体形态描述符的地位，使得集合体应该由参数D-f和k(0)对来描述，即(D-f，k(0))。
Motivated by recent experiments of soot formation in premixed flames where a minority population of the "stringy" aggregates is found to have a fractal dimension as low as 1.2 instead of the classic diffusion-limited cluster-cluster aggregation (DLCA) value of 1.8, we address this same question in our simulation study: is there a distribution of fractal dimensions in a given ensemble of aggregates and does shape anisotropy of clusters control the fractal dimension? Our results, however, clearly show classic DLCA yields aggregates of a broad range of shapes all with D-f approximate to 1.8 independent of their shape, but with a shape dependent pre-factor k(0), in the relation between radius of gyration R-g, mass N, monomer radius a, and fractal dimension D-f, N = k(0)(Rg/a)(Df). Thus the pre-factor k(0) gains in status as a descriptor of aggregate morphology so that aggregates should be described by the pair of parameters D-f and k(0), i.e., (D-f, k(0)).