Monte Carlo simulations of partially ionized polyelectrolytes: Shape and distribution functions

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Abstract
A novel modification to the ‘‘slithering snake’’ algorithm is used to enable Monte Carlo simulations of partially ionized polyelectrolyte chains where the charged beads interact via screened Coulomb interactions. The use of ‘‘stroboscopic’’ averaging enables detailed shape characteristics of the chains to be calculated. The moment of inertia tensor, the distribution function of the end-to-end distance and the segment density distribution functions from the center of mass and both ends of the polyion are combined to give an overall characterization of the shape changes of a polyion as added salt concentration, chain length (up to 240 beads) and degree of ionization are varied. Some abrupt behavior seen for high degree of ionization may be smoothed once ionic degrees of freedom are included. The present work—by characterizing the shape of short chains—may also help to formulate models for very long polyions consisting of many segments, each of a few hundred beads.