Small gold clusters on graphene, their mobility and clustering: a DFT study

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Experimentally observed high mobility and clustering of gold atoms on graphene.
• Need for theoretical understanding of gold cluster formation and behavior on surfaces.

Purpose of the Study:

• Investigate ground state structures of small gold clusters on graphene using density functional theory.
• Analyze the mobility and clustering mechanisms of gold adatoms and clusters on graphene.
• Identify driving forces for gold aggregation on graphene.

Main Methods:

• Density functional theory (DFT) calculations.
• Analysis of electronic structures.
• Study of adsorption energies and diffusion barriers.

Main Results:

• Identified strong gold-gold bonds and graphene-mediated interactions as key drivers for gold aggregation.
• Determined unique ground state structures for gold clusters up to four atoms on graphene, with Au(4)(Y) being favored over Au(4)(D).
• Found all studied clustering reactions to be exothermic with negligible activation barriers beyond diffusion.

Conclusions:

• Gold atom mobility on graphene is high due to low diffusion barriers (4-36 meV) significantly lower than adsorption energies (-0.1 to -0.59 eV).
• Graphene's electronic structure facilitates strong inter-gold bonding and mediates interactions, promoting cluster formation.
• The study explains the observed experimental phenomena of gold atom mobility and nanocluster formation on graphene surfaces.