Diffusion-limited aggregates grown on nonuniform substrates

In the present paper, patterns of diffusion-limited aggregation (DLA) grown on nonuniform substrates are investigated by means of Monte Carlo simulations. We consider a nonuniform substrate as the largest percolation cluster of dropped particles with different structures and forms that occupy more than a single site on the lattice. The aggregates are grown on such clusters, in the range the concentration, p , from the percolation threshold, p c up to the jamming coverage, p j . At the percolation threshold, the aggregates are asymmetrical and the branches are relatively few. However, for larger values of p , the patterns change gradually to a pure DLA. Tiny qualitative differences in this behavior are observed for different k sizes. Correspondingly, the fractal dimension of the aggregates increases as p raises in the same range p c ≤ p ≤ p j . This behavior is analyzed and discussed in the framework of the existing theoretical approaches.