Computer Simulation of a Hard-Rod System: Structural Transitions and Clusters

We have studied by computer simulation a continual 2D hard-rod system with volume topological interaction between the rods. The microstructure of the rods that is obtained can be conveniently analyzed with the help of cluster formation terminology. We have shown that cluster distribution with respect to the numbers of rods can be written as P(N) identical with A sub(0) exp[(A sub(1))N], where A sub(0) and A sub(1) are constants which depend upon the cluster forming criteria and the rod system density, rho , and N is the number of rods in a cluster. There are two transition regions in the hard-rod system of 2D spherocylinders at the axes ratio p identical with 6. The transition at rho identical with 0.35-0.40 is the structural transition from the intermediate solution of rods and clusters to the solution of overlapped rods and clusters. The transition at rho identical with 0.50-0.55 can be associated with the appearance in the system of percolation clustering. The cluster in the 2D rod system can therefore be considered to be a quasi-rod. The implication of this is that thermodynamic calculations for the system should be carried out as they would be for a polydisperse system with a given distribution of quasi-rods.