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O: Fachverband Oberflächenphysik

O 40: Solid-Liquid Interfaces

O 40.11: Poster

Dienstag, 17. März 2015, 18:15–21:00, Poster A

Dynamics of water adsorption on Pt(111): ab initio molecular dynamics study — •Maryam Naderian and Axel Groß — Institute of Theoretical Chemistry, Ulm University, D-89069 Ulm/Germany

Ab initio molecular dynamics (AIMD) simulations based on periodic density functional theory (DFT) calculations using the dispersion-corrected RPBE-D3 functional [1] have been performed to study the dynamics of adsorption and sticking probability of water molecules on Pt(111). As typical for molecular adsorption, the sticking probability has been found to decrease as a function of the initial kinetic energy (IKE) of the impinging water molecules. Special attention has been paid to the role of the internal degrees of freedom of the water molecules upon impinging on the Pt substrate. Most of the IKE of the water molecule is initially transferred into the internal molecular degrees of freedom (vibrations and rotations) and later to the kinetic energy of the substrate atoms [2]. This energy redistribution leads to an efficient dissipation of the initial energy of water molecule which is crucial for understanding molecular adsorption dynamics.

To shed some light on the dynamics of the initial water structure formation on metal electrodes, we have performed AIMD simulations of water molecules impinging on Pt(111) that is already precovered by water. Again analysing the energy redistribution upon adsorption, the physical factors which are responsible for the water structure formation on a Pt surface are identified.

[1] S. Grimme et al., J. Comput. Chem. 32, 1456 (2011).

[2] Axel Groß et al., J. Electrochem. Soc. 161, E3015-E3020 (2014).