Eden growth model for aggregation of charged particles

The stochastic Eden model of charged particles aggregation in two-dimensional systems is presented. This model is governed by two parameters: screening length of electrostatic interaction, $\lambda$, and short range attraction energy, $E$. Different patterns of finite and infinite aggregates are observed. They are of following types of morphologies: linear or linear with bending, warm-like, DBM (dense-branching morphology), DBM with nucleus, and compact Eden-like. The transition between the different modes of growth is studied and phase diagram of the growth structures is obtained in $\lambda, E$ co-ordinates. The detailed aggregate structure analysis, including analysis of their fractal properties, is presented. The scheme of the internal inhomogeneous structure of aggregates is proposed.Comment: Revtex, 9 pages with 12 postscript figure

Percolation of the aligned dimers on a square lattice

Percolation and jamming phenomena are investigated for anisotropic sequential deposition of dimers (particles occupying two adjacent adsorption sites) on a square lattice. The influence of dimer alignment on the electrical conductivity was examined. The percolation threshold for deposition of dimers was lower than for deposition of monomers. Nevertheless, the problem belongs to the universality class of random percolation. The lowest percolation threshold (pc = 0.562) was observed for isotropic orientation of dimers. It was higher (pc = 0.586) in the case of dimers aligned strictly along one direction. The state of dimer orientation influenced the concentration dependence of electrical conductivity. The proposed model seems to be useful for description of the percolating properties of anisotropic conductors.Comment: 6 pages, 9 figures, submitted to EPJ

Deterministic growth model of Laplacian charged particle aggregates

The results of the computer simulation of the aggregates growth of the similarly charged particles in the framework of deterministic Laplacian growth model on a square lattice are presented. Cluster growth is controlled by three parameters ${p, E,\lambda}$, where $p$ - Laplacian growth parameter, $E$ - energy of a particle sticking to a cluster, $\lambda$ - the screening length of electrostatic interactions. The phase diagram of cluster growth is built in the co-ordinates ${E,\lambda}$. The zones of different cluster morphology are selected: I-the zone of finite X-like structures,II-the zone of infinite ramified structures, controlled by electrostatic interactions, III-the zone of infinite structures with electrostatic interactions effectively switched off. Simple electrostatic estimations of the locations of the zone boundaries are presented. It is shown that in general case within the zone II the continuous change of $D_f$, controlled by parameters ${p, E,\lambda}$, takes place. In the degeneration limit when the given model transforms into deterministic version of the Eden model (at $p=0$), the crossover from linear $(D_f=1)$ to compact $(D_f=2)$ structures is observed when passing through the boundary between the zones I and II.Comment: REVTEX, 3 pages with 4 postscript figure

How the geometry makes the criticality in two - component spreading phenomena?

We study numerically a two-component A-B spreading model (SMK model) for concave and convex radial growth of 2d-geometries. The seed is chosen to be an occupied circle line, and growth spreads inside the circle (concave geometry) or outside the circle (convex geometry). On the basis of generalised diffusion-annihilation equation for domain evolution, we derive the mean field relations describing quite well the results of numerical investigations. We conclude that the intrinsic universality of the SMK does not depend on the geometry and the dependence of criticality versus the curvature observed in numerical experiments is only an apparent effect. We discuss the dependence of the apparent critical exponent $\chi_{a}$ upon the spreading geometry and initial conditions.Comment: Uses iopart.cls, 11 pages with 8 postscript figures embedde