Towards a specific reaction parameter density functional for reactive scattering of H2 from Pd(111)

Area of Science:

• Surface science
• Computational chemistry
• Physical chemistry

Background:

• The specific reaction parameter (SRP) approach within density functional theory (DFT) has successfully modeled activated hydrogen molecule (H2) dissociation on copper surfaces.
• Investigating H2 dissociation on palladium surfaces is crucial for understanding non-activated reactions on metal catalysts.

Purpose of the Study:

• To assess the applicability of the SRP-DFT methodology to non-activated H2 dissociation on a Pd(111) surface.
• To compare theoretical calculations with experimental molecular beam sticking data for H2 + Pd(111).

Main Methods:

• Utilized the SRP-DFT methodology with Born-Oppenheimer static surface approximations.
• Employed the PBE-vdW functional for reactive scattering calculations.
• Compared quantum dynamics calculations with experimental sticking probabilities.

Main Results:

• The PBE-vdW functional showed promise for modeling H2 scattering on Pd(111) at higher energies (≥125 meV).
• Quantum dynamics calculations failed to reproduce experimental results at lower incidence energies (<125 meV).
• Dynamic trapping and steering effects were identified as significant but not well-modeled by current potential energy surfaces.

Conclusions:

• Applying SRP-DFT to non-activated H2 dissociation remains challenging.
• A density functional with broader barrier distributions and more non-activated pathways is needed for accurate modeling.
• Further experimental data from well-characterized molecular beam sticking experiments on H2 + Pd(111) are recommended.