Exact relationship between the radius of gyration and the density-density correlation function: Application to diffusion limited aggregation

1990 ◽  
Vol 163 (2) ◽  
pp. 433-439 ◽  
Author(s):  
Daniel E. Platt ◽  
Fereydoon Family
2012 ◽  
Vol 26 (29) ◽  
pp. 1250146 ◽  
Author(s):  
BHASKAR SEN GUPTA ◽  
SHANKAR P. DAS

The renormalized dynamics described by the equations of nonlinear fluctuating hydrodynamics (NFH) treated at one loop order gives rise to the basic model of the mode coupling theory (MCT). We investigate here by analyzing the density correlation function, a crucial prediction of ideal MCT, namely the validity of the multi step relaxation scenario. The equilibrium density correlation function is calculated here from the direct solutions of NFH equations for a hard sphere system. We make first detailed investigation for the robustness of the correlation functions obtained from the numerical solutions by varying the size of the grid. For an optimum choice of grid size we analyze the decay of the density correlation function to identify the multi-step relaxation process. Weak signatures of two step power law relaxation is seen with exponents which do not match predictions from the one loop MCT. For the final relaxation stretched exponential (KWW) behavior is seen and the relaxation time grows with increase of density. But apparent power law divergences indicate a critical packing fraction much higher than the corresponding MCT predictions for a hard sphere fluid.


2016 ◽  
Vol 71 (3) ◽  
pp. 225-234
Author(s):  
Tugba Ozbey ◽  
Mehmet Bayirli

AbstractThe formation mechanisms and the origin of manganese dendrites on the magnesite ore have been under discussion. The growth process of the manganese dendrites is statistically studied by comparing them to aggregations obtained according to the diffusion limited aggregation (DLA) model via Monte Carlo simulations. In this case, ten manganese dendrite patterns changing from the least dense to the densest aggregations on the surface are separately selected to determine the relationship between real and simulated patterns. The sticking parameter is ranged from 0.05≤t≤1. The density–density correlation functions C(r) (their critical exponent A), fractal dimension Df, critical exponent α, and critical exponent β pertaining to the root mean square (rms) thickness have been computed for both the ten manganese dendrites and the simulated aggregations representing them. The results indicate that manganese dendrites may be determined with the general DLA model. Analyses of manganese dendrites, both scaling and simulations, suggest the growth mechanism for the macroscopic expression of crystalline anisotropy for the dendritic patterns. These results are in good agreement with the values in other literature and can be helpful in comparing natural and simulated aggregations (both dendritic and compact deposits).


1990 ◽  
Vol 68 (9) ◽  
pp. 1099-1104
Author(s):  
Mark F. Schumaker ◽  
Irving R. Epstein

We develop a simple model for the aggregation of telechelic ionomers by extending the well-known algorithm for particle diffusion-limited aggregation (DLA). The distribution of sticky and nonsticky regions of the polymer and specific rules for binding are incorporated. Thirteen aggregates are grown to a final size of 2441 polymers each. The distribution of accessible binding sites modifies the growth of these clusters as compared with DLA. The dynamical dimension estimated from the growth of the radius of gyration is found to have a value of 1.81 ± 0.04, significantly larger than values reported for particle DLA. However, a careful analysis of our data suggests that the dimension is nonstationary and decreasing at the largest cluster sizes attained. We have also investigated the scaling of the average mass of the cluster interface with the number of polymers and the radius of gyration. Our results suggest that the fractal dimension of the cluster interface is close to one, in agreement with previously reported findings for particle DLA.


1988 ◽  
Vol 196 (1-3) ◽  
pp. 487-493 ◽  
Author(s):  
R.Q. Yang ◽  
X.J. Lu ◽  
X.L. Lei ◽  
L.M. Xie ◽  
C.H. Tsai

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