Simulated videos of radial Liesegang patterns
On this page I have collected some nice simulated videos of radial Liesegang patterns.
Click on the film icons to play the corresponfing MPEG-1 video!
Effects and anomalies in 2D
Computations shown here were all performed with the ReaDiVivus system using the IDNB model of periodic precipitation. Because ReaDiVivus is capable to solve stochastic differential equations it was possible to take into account the effect of various randomizing impacts.
The "twins" - spiral formation
Although simulations shown videos No. 1. and No. 2. had completely identical input parameters the first structure is regular while the second is a two-armed spiral. It is important to stress that this structural distortion is caused by a stochastic resonance and not by the asymmetry of the initial conditions.
Dilute sol between the zones
On videos No. 3. and No. 4. it can be clearly seen that depending on the imput parameters in certain patterns the gaps between the precipitated region are filled with a dilute sol. According to the literature this has been often found in real experiments too. Formerly this finding was the basis of the sol-coagulation model and all so-called postnucleation theories.
This video shows a revert structure in which case the distance between adjacent bands decreases during the development until finaly the distribution becomes continuous.
Successfull description of this anomalous patterning trend was one of the greatest unsolved mysteries of Liesegang patterning. It could not be reproduced by any of the formerly suggested models.
On real chemical patterns one can often observe various local distortions that are intorduced by random impacts. Whether the effect of these impacts remains local or propagates further in the structure depends on the dynamics of patterning. In case of Liesegang patterns the randomizing effect is amplified by the mechanism in certain parameter ranges and a so-called stochastic resonance appears in the system.
These two videos show the development of such propagating defects that normally span the whole pattern. At the same time similar resonances appear in the former revert pattern too, but they disappear after a while. This is a general effect, that is revert patterning facilitates "wound healing" even if the final distribution is not continuous (partially revert pattern).
Video No. 8. shows the development of a two-centered system. At the region where the two ring systems bump into each other their interference results in a roughly hexagonally symmetric patchy pattern.