Surface charge regulation using classical density functional theory: the effect of divalent potential determining
Nathalia Salles Vernin1, Dirk Gillespie2
1Department of Sanitary and Environmental Engineering, Rio de Janeiro State University, Rio de Janeiro, RJ 20550-900, Brazil. nathalia.vernin@eng.uerj.br.
Physical Chemistry Chemical Physics : PCCP
|December 19, 2022
Summary
Divalent ion size significantly impacts surface charge density, contrary to point-ion assumptions. Ion correlations, crucial at high concentrations, lead to charge inversion, a phenomenon missed by traditional models.
Area of Science:
- Surface chemistry
- Physical chemistry
- Computational chemistry
Background:
- Charge regulation models describe surface charge influenced by protons and ions.
- Conventional Poisson-Boltzmann (PB) equation neglects ion size and electrostatic correlations.
- Classical density functional theory (DFT) incorporates these correlations.
Purpose of the Study:
- Investigate the role of divalent ions in surface charge regulation.
- Assess the impact of divalent ion size on surface charge density.
- Explore ion correlation effects in divalent ion-surface interactions.
Main Methods:
- Coupling charge regulation with classical density functional theory (DFT).
- Utilizing DFT to explicitly include ion size and electrostatic correlations.
- Comparing DFT results with Poisson-Boltzmann theory.
Main Results:
- Divalent ion size significantly influences surface charge density; it should not be neglected.
- Larger divalent cations lead to greater surface charge due to higher local concentrations.
- Ion correlations play a non-negligible role at low concentrations and a dominant role at high concentrations, causing charge inversion.
Conclusions:
- DFT provides a more accurate description of charge regulation with multivalent ions than PB theory.
- Divalent ion size is a critical parameter for understanding surface charge.
- Ion correlations are essential for accurately modeling surface charge phenomena, especially at higher concentrations.
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