LARGE-CELL RENORMALIZATION-GROUP AND ORDER-PARAMETER FOR SITE PERCOLATION PROBLEMS

We point out that in the large cell-to-cell renormalization-group transformations to obtain the thermodynamic free energy and order parameter of a phase-transition system, we need only iterate the transformations until the correlation length of the system is smaller than the linear dimensions of the cells. We apply this idea to obtain a very accurate order parameter for the site-random percolation model, which may be used to represent dilute magnets at low temperatures. © 1995 The American Physical Society.