| Abstract
| - The techniques of canonical Monte Carlo simulations are employed in a comparative study of two recentlyproposed criteria for the determination of the renormalized or effective charge of a spherical macroion ina charge-stabilized colloidal suspension. The effective charge is determined using (i) the thermal criterion,where the effective charge consists of the intrinsic macroion charge reduced by the integratedthermodynamically bound counterion charge, the bound counterions being defined as those counterionsthat are within and up to the radial distance (from the macroion center) at which the reduced meanelectrostatic potential energy equals the thermal energy, and (ii) the concentration criterion, where thebound counterions are those that lie within the distance at which the local concentration of the counterionsequals its average value. It is found that the former criterion applies to the entire range of bare macroioncharge/macroion radius ratios investigated, whereas the latter criterion is more suited to large values ofthis ratio. The observation that the effective charge/bare charge ratio (Zeff/Zm) depends only on the barecharge/macroion radius ratio (Zm/rm) suggests that all macroions with the same numerical value of theZm/rm ratio are “equivalent systems” and that one can therefore study highly charged colloids by usinga more manageable set of parameters in a simulation. The calculations are extended to divalent counterionsystems, and comparisons are also made with other criteria for determining the effective macroion chargein the literature.
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