摘要(英) |
At strong electrostatic coupling, counterions are accumulated in the vicinity of the surface of the
charged particle with intrinsic charge Z. In order to explain the behavior of highly charged particles,
effective charges Z* is therefore invoked in the models based on Debye-Hückel approximation, such
as the DLVO potential. For a salt-free colloidal suspension, we perform Monte Carlo simulations to
obtain various thermodynamic properties ω in a spherical Wigner-Seitz cell. The effect of dielectric
discontinuity is examined. We show that at the same particle volume fraction, counterions around
a highly charged spheres with Z may display the same value of ω as those around a weakly charged
sphere with Z*, i.e., ω(Z) = ω(Z*). There exists a maximally attainable value of ω at which
Z = Z*. Defining Z* as the effective charge, we find that the effective charge passes through a
maximum and declines again due to ion-ion correlation as the number of counterions is increased.
The effective charge is even smaller if one adopts the Debye-Hückel expression ωDH. Our results
suggest that charge renormalization can be performed by chemical potential, which may be observed
in osmotic pressure measurements. |
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