Abstract:
In this work, we present 2D Monte Carlo simulations of tracer in disorder media with
obstacles distributed randomly. For diffusion of a particle, the mean-square displace
ment of the diffusing species is linearly proportional to time for normal diffusion.
But in disordered systems anomalous diffusion occurs, in which the means square
displacement is proportional to a fractional power of time not equal to one.As the ob
stacle concentration approaches the percolation threshold, diffusion becomes more
anomalous for long times; the anomalous diffusion exponent increases.Simulation
data show anomalous for short times and normal for long times below percolation
threshold.Monte Carlo calculations are used to characterize anomalous diffusion for
obstacle concentrations between zero and the percolation threshold.In addition,above
percolation threshold anomalous for short times but for long time( t), < r2 > approx
imate fixed point proportional to mean value of boundary condition.,So the slope
oflog < r2 > /t versus logt goes to-1 and dw →.The intersection time from normal
to crowded diffusion is the crossover time tCR.
