Oxygen adsorption on beta-cristobalite polymorph: ab initio modeling and semiclassical time-dependent dynamics

Area of Science:

• Materials Science
• Surface Chemistry
• Computational Chemistry

Background:

• Understanding atomic and molecular oxygen interactions with silica is crucial for catalysis and semiconductor manufacturing.
• Beta-cristobalite is a key silica polymorph relevant to various industrial applications.

Purpose of the Study:

• To investigate the adsorption dynamics of atomic and molecular oxygen on a model beta-cristobalite silica surface.
• To determine the interaction potentials and adsorption mechanisms using computational methods.

Main Methods:

• Ab initio electronic structure calculations using Density Functional Theory (DFT).
• Semiclassical molecular dynamics simulations.
• Evaluation of binding energies and adsorption barriers.

Main Results:

• Atomic oxygen (O) exhibits strong chemisorption with a binding energy of 5.57 eV.
• Molecular oxygen (O2) shows weak adsorption with a high energy barrier (~2 eV).
• Adsorption is primarily governed by single-bounce collisions, with a small probability for multi-collision mechanisms.

Conclusions:

• The O-silica interaction is local, depending on the specific site.
• A complex multiphonon excitation-deexcitation mechanism underlies adsorption and reflection collisions.
• Reflection collisions, though having small probabilities, are non-negligible at higher impact energies.