Hydrogen atom adsorption on aluminum icosahedral clusters: A DFT study

Properties of hydrogenated, icosahedral aluminum clusters were investigated using density functional theory in comparison with those of aluminum bulk systems. The most stable site for H adsorption to Al13 was the hollow HCP site. The H binding energy suggests that the top and the bridge configurations are transition states. Results for Al13H were compared with those obtained for two surface models simulating f.c.c. and icosahedral (1 1 1) surfaces. Results show that the H atom interacts weakly with surface of clusters when the cluster size is increased. The migration energy of H atom between neighboring T and O sites becomes smaller for icosahedral subsurface than for either bulk material or the f.c.c. subsurface. A similar relation between the two surface models was found for the migration energy between surface and subsurface sites. These results indicate that the icosahedral surface lowers the migration barriers of H atom both within the subsurface and between the surface and the subsurface.

Graphical abstract. Energy barriers for H atom migrating from the interstitial sites to surface adsorption sites for f.c.c. Al(1 1 1) surface and icosahedral surface. The icosahedral surface lowers the migration barriers of H atom both within the subsurface and between the surface and the subsurface.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ Energetic properties of aluminum clusters absorbed with hydrogen atoms were investigated for the “magic” clusters with icosahedral symmetry based on the first-principles calculation. ▶ The slab model is made for representing the surface of icosahedral clusters by deforming the f.c.c. surface model. ▶ The hydrogen diffusion barriers are calculated for interstitial sites of aluminum clusters and compared to those of bulk aluminum system. ▶ The icosahedral surface lowers the migration barriers to H atoms between the surface and subsurface compared to the f.c.c. surface.