Gold Clusters on Graphene/Graphite-Structure and Energy Landscape.

Adopting an advanced microscopic model of the Au-graphite interaction, a systematic study of Au nanoclusters (up to sizes of 11 238 atoms) on graphene and on graphite is carried out to explore their structure and energy landscape. Using parallel tempering molecular dynamics, structural distribution as a function of temperature is calculated in the entire temperature range. Low-energy structures are identified through a combination of structural optimization and Wulff-Kaischew construction which are then used to explore the energy landscape. The potential energy surface (PES), which is energy as a function of translation and rotation, is calculated for a few Au nanoclusters along specific directions on carbon lattice. Minimum-energy pathways are identified on the PES indicating a reduced barrier for pathways involving simultaneous rotation and translation. Diffusion simulations of Au on graphite show that diffusion mechanism is directly related to the PES, and the information of the cluster pinning events is already present in the PES. Finally, a comparison of various interaction models highlights the importance of reasonably correct Au-C interactions which is crucial for studying the energy landscape and cluster sliding.