Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 36: Complex Fluids and Soft Matter 2 (joint session DY/CPP)

CPP 36.1: Talk

Thursday, September 8, 2022, 10:00–10:15, H18

Underscreening in the Restricted Primitive Model — •Andreas Härtel — Institute of Physics, University of Freiburg, Germany

Electric double layers occur where charges are screened by other charges, for instance, when charged surfaces of electrodes, colloids, or cells are exposed to electrolytes (mobile ions in a solvent). Increasing the concentration of mobile ions leads to more efficient screening, if concentrations are sufficiently low. At high concentrations, however, the screening by finite-sized ions becomes less efficient than those of point-like ions due to packing, an effect called underscreening. Some experiments report underscreening as a strong effect that follows some universal scaling [1], but the observation could not been explained by theoretical models yet. Conversely, independent theoretical studies actually ruled out the most important model for electrolytes of finite-sized ions as a candidate able to explain underscreening, namely the restricted primitive model [2]. In this talk I will discuss in which sense underscreening can and cannot be found in the restricted primitive model and in which sense the effect follows some universal scaling. I will support the discussion by recent theoretical results obtained from simulations and liquid state theories.

[1] Lee et al., Underscreening in concentrated electrolytes, Faraday Dicuss. 199, 239 (2017).

[2] Cats et al., Primitive Model Electrolytes in the Near and Far Field: Decay Lengths from DFT and Simulations, J. Chem. Phys. 154, 124504 (2021).