A CLUSTER-CLUSTER AGGREGATION MODEL WITH TUNABLE FRACTAL DIMENSION

A hierarchical cluster-cluster aggregation computer model is introduce d which allows one to build random fractal aggregates on a d-dimension al lattice with a fractal dimension fixed a priori. The algorithm work s iteratively by sticking aggregates of the same number of particles a t the correct centre-to-centre distance in order to recover the desire d scaling. With the more efficient versions of the model, any fractal dimension ranging from 1 up to a d-dependent upper limit D(M)(d) can b e obtained. One estimates D(M)(2) congruent-to 1.80 +/-0.03 and D(M)(3 ) congruent-to 2.55 +/- 0.04. Calculations up to d = 6 show that the r atio D(M)(d)/d decreases as d increases.