SIMULATIONS ON THE PRIMITIVE ELECTROLYTE ENVIRONMENT OF A HIGH CHARGE-DENSITY POLYELECTROLYTE. A SAMPLING PROBLEM AND ITS SOLUTION

We show that the classical Metropolis Monte Carlo (MMC) algorithm converges very slowly when applied to the primitive electrolyte environment for a high charge-density polyelectrolyte. This slowness of convergence, which is due to the large density inhomogeneity around the polyelectrolyte, produces noticeable errors in the ion distribution functions for MMC runs of 1.3 x 10(6) trial steps started from nonequilibrium distributions. We report that an algorithm which we call DSMC (for density-scaled Monte Carlo) overcomes this problem and provides relatively rapid convergence in this application. We suggest that DSMC should be well-suited for other Monte Carlo simulations on physical systems where large density inhornogeneities occur.