Adsorption dynamics of H2 on Pd(100) from first principles

Area of Science:

• Surface Science
• Physical Chemistry
• Computational Materials Science

Background:

• Understanding molecule-surface interactions is crucial for catalysis and materials design.
• Hydrogen dissociative adsorption on metal surfaces is a fundamental process with implications for various chemical reactions.

Purpose of the Study:

• To investigate the dissociative adsorption of H2 on Pd(100) using classical molecular dynamics (MD).
• To analyze the influence of initial rotational states (J) on adsorption probabilities.
• To compare the accuracy and efficiency of ab initio MD (AIMD) and interpolated potential energy surface (PES) methods.

Main Methods:

• Classical molecular dynamics (MD) simulations.
• Density functional theory (DFT) for calculating molecule-surface interaction potentials.
• Two force evaluation methods: direct DFT calculations (AIMD) and using a pre-computed, interpolated six-dimensional potential energy surface (CRP-PES-MD).

Main Results:

• AIMD and CRP-PES-MD methods yield very similar dissociative adsorption probabilities (P(diss)) for low rotational states (0 ≤ J ≤ 4).
• P(diss) shows minimal dependence on J for impact energies (E(i)) above 200 meV.
• At low energies, P(diss) exhibits a non-monotonic J-dependence, influenced by competing shadowing effects (decreasing P(diss) with increasing J for low J) and rotational-to-translational energy transfer (increasing P(diss) with increasing J for J > 6).

Conclusions:

• The interpolated CRP-PES provides a reliable and computationally efficient representation of the ab initio PES for H2/Pd(100) dissociative adsorption.
• Rotational effects play a significant role in H2 dissociative adsorption dynamics, particularly at low impact energies.
• The study confirms the operation of competing dynamical effects (shadowing and energy transfer) in a realistic high-dimensional system.