Adsorption of Li, Na, K, and Mg atoms on amorphous and crystalline silica bilayers on Ru(0001): A DFT study

The interaction of Li, Na, K, and Mg atoms with crystalline and amorphous silica bilayers grown on Ru(0001) supports has been studied by performing DFT calculations. (Si4O6H4) clusters have been chosen to represent different ring sizes (n = 4-8) of amorphous silica bilayers. We found that, on unsupported silica films, the alkali metal atoms adsorb as neutral entities with weak adsorption energies, whereas the diffusion into the cage is not thermodynamically favorable. Interaction of Na with Al-doped silica cages has also been investigated. The presence of this Al dopant enhances the strength of the metal-framework interaction, changing completely the bonding mechanism that is dominated by charge transfer contributions. Na and Mg interacting with a crystalline silica bilayer on a 3O(2 x 2)/Ru(0001) surface adsorb preferentially at the interface between the support and the silica film with high adsorption energies and transfer their valence electrons to the Ru metal.