Density functional study of small neutral and charged silver cluster hydrides

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Silver clusters are of interest due to their unique electronic and catalytic properties.
• Understanding the interaction of hydrogen with silver clusters is crucial for catalysis and materials design.

Purpose of the Study:

• To investigate the structural and electronic properties of neutral, anionic, and cationic silver cluster hydrides (AgnH and HAgnH).
• To determine the preferred adsorption sites and stability of hydrogen atoms on silver clusters of varying sizes and charges.

Main Methods:

• Utilized the PW91PW91 density functional method for theoretical calculations.
• Employed Natural Bond Orbital (NBO) analysis to understand electronic structure and charge transfer.

Main Results:

• The most stable structures of silver cluster hydrides do not always derive from the most stable bare silver clusters.
• Energetically preferred hydrogen adsorption sites vary: bridge site for cationic and most neutral clusters, top site for smaller anionic clusters (n<=4), and bridge site for larger anionic clusters.
• In anionic HAgnH clusters, the lowest energy structures feature both hydrogen atoms bonded to a single silver atom.
• Electron transfer consistently occurs from silver atoms to the hydrogen adsorbate, regardless of charge state.
• Observed a significant odd-even alternation in binding strength, with hydrogen binding more strongly to odd-electron bare clusters.

Conclusions:

• The binding behavior of hydrogen on silver clusters is complex and highly dependent on cluster size, charge, and specific adsorption site.
• Density functional theory and NBO analysis provide valuable insights into the electronic interactions governing silver-hydrogen cluster systems.
• The findings contribute to the fundamental understanding of metal-hydrogen interactions, relevant for catalysis and nanostructure design.