Regensburg 2025 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Poster Session II
CPP 32.34: Poster
Donnerstag, 20. März 2025, 09:30–12:00, P3
Classical simulation studies of dissociation equilibria in nanoconfined systems — •Kira Fischer, Henrik Stooß, and Alexander Schlaich — Institute for Atomistic Modeling of Materials in Aqueous Media, Hamburg University of Technology, Germany
Dissociation equilibria in nanoconfinement are relevant to the chemistry of nanostructured catalysts, aerosols and protein pockets. Experiments indicate that nanoconfinement affects the dissociation of water, however to date a comprehensive understanding is still lacking. Here, we investigate dissociation equilibria in nanoconfinement from a classically. Using molecular dynamics and free energy methods we study hydrochloric acid in diamond nanoconfinement in the dilute limit at ambient conditions.
Our studies reveal a depletion of hydrochloric acid in nanoconfinement, with a negative excess by up to a factor of 100. The negative excess is attributed to the balance between hydronium adsorption and chloride depletion at the interface. Additionally, we propose that hydronium is adsorbed to the diamond interface by dipole orientation within a local electric field. Notably, in the smallest pore, the pKa is increased by 1. We also introduce useful concepts for analysing dissociation equilibria in confinement. This includes the chemical potential in confinement, which enables quantification of ionic excess in the dilute limit. Furthermore, we demonstrate how to derive the chemical potential from the potential of mean force, thereby decomposing the different energetic contributions to the excess chemical potential.
Keywords: chemical equilibrium; free energy methods; dissociation; nanoconfinement; water interfaces