The structure transition in cluster-cluster aggregation (CCA) under different external electric fields has been investigated by computer simulations. The aggregates are generated from off-lattice CCA models involving the field-induced dipolar interactions and temperatures by means of a Metropolis algorithm. When the parameter K increases from 0 to ∞, the clusters gradually change from a diffusion-limited CCA to a chainlike pattern, where K stands for the relative strength of the field-induced dipolar interaction with thermal energy. The relation of fractal dimension $D_f$ to parameter K can be approximately expressed as $D_f{=D}_E{+(D}_{\mathrm{DLCA}}-D_E{)e}^{-\beta K}$ with $\beta =0.64,$ where $D_E$ and $D_{\mathrm{DLCA}}$ stand for the fractal dimensions of the CCA when $\overrightarrow{K}\infty$ and $\overrightarrow{K}0,$ respectively. This structure transition is a transition between a prototype disorder structure and a relative order one. The transition is attributed to the variation of the dominating interaction of systems from thermal disorder to field-induced dipolar interaction with K rising.

• Received 7 December 1999

DOI:https://doi.org/10.1103/PhysRevE.62.734