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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 21: French-German Session: Simulation Methods and Modeling of Soft Matter III
CPP 21.2: Talk
Tuesday, March 10, 2026, 10:00–10:15, ZEU/0255
Classical DFT compared to AFM measurement of structural forces from confined electrolyte containing charged nanoparticles — •Simone Riva1, Michael Ludwig2, Regine von Kltizing2, and Ofer Manor1 — 1Technion, Haifa, Israel — 2Technische Universität Darmstadt, Darmstadt, Germany
We use classical density functional theory (DFT) to model colloidal-probe atomic force microscopy (AFM) force curves across an aqueous electrolyte containing charged solid nanoparticles. The charged AFM probe and substrate interact through a suspension of silica nanoparticles. The probe experiences oscillatory forces driven by the structuring of the charged nanoparticles, which can enhance the stability of the film. Structural forces are characterized by an alternation of repulsion due to steric and electrostatic nanoparticle interactions, and depletion attraction. We present a self-consistent theory of oscillatory forces in ionic systems. Moreover, we compare different DFT approaches and validate them against AFM measurements, to develop a theory that best fits the rich physics of experiments. We calculate structural and EDL forces by minimizing dedicated functionals. We adopt two types of weighted density functionals, disclosing their applicability in different concentration conditions. We propose a way to include electrostatic interactions between nanoparticles in an effective hard-sphere functional. We further confirm a general scaling law of the oscillation wavelength observed in experiments and connect it to nanoparticle packing structures. The theory agrees well with measurement in the absence of fitting parameters. Riva et al., JCIS 2026, 702, 138901.
Keywords: Classical density functional theory; Atomic force microscopy; Complex liquids; Structural forces