Berlin 2024 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 16: Modeling and Simulation of Soft Matter II
CPP 16.10: Vortrag
Dienstag, 19. März 2024, 12:15–12:30, H 0106
Thermal dependence of the hydrated proton and optimal proton transfer in the protonated water hexamer — •Michele Casula1, Félix Mouhat2, Matteo Peria1, Tommaso Morresi3, Rodolphe Vuilleumier4, and A. Marco Saitta1 — 1IMPMC, Sorbonne Université, CNRS, MNHN, Paris, France — 2Saint Gobain Research Paris, Aubervilliers, France — 3ECT*-Fondazione Bruno Kessler*, Trento, Italy. — 4PASTEUR, École normale supérieure, Paris, France
Water is a key ingredient for life and plays a central role as solvent in many biochemical reactions. However, the intrinsically quantum nature of the hydrogen nucleus, revealing itself in a large variety of physical manifestations, including proton transfer, gives rise to unexpected phenomena whose description is still elusive. Here we study, by a combination of state-of-the-art quantum Monte Carlo methods and path-integral molecular dynamics, the structure and hydrogen-bond dynamics of the protonated water hexamer, the fundamental unit for the hydrated proton. We report a remarkably low thermal expansion of the hydrogen bond from zero temperature up to 300 K, owing to the presence of short-Zundel configurations, characterised by proton delocalisation and favoured by the synergy of nuclear quantum effects and thermal activation. The hydrogen bond strength progressively weakens above 300 K, when localised Eigen-like configurations become relevant. Our analysis, supported by the instanton statistics of shuttling protons, reveals that the near room-temperature range from 250 K to 300 K is optimal for proton transfer.
Keywords: protonated water cluster; path-integral molecular dynamics; quantum Monte Carlo; proton transfer; liquid water