The effects of Pt doping on the optical properties of Au20

We consider the doping of Pt onto small Au-20 clusters, identifying the effects that this alloying has upon the optical and static properties of each candidate nanoalloy. By performing real-time time dependent density functional theory calculations, we determine that the electronic structure and, by extension, the optical absorption spectrum strongly depend on the position of a Pt dopant; either as substitutional defect, or as an adsorbed atom on the Au-surface. Indeed, we find that by varying the local positions, we are able to strongly influence the electronic and optical properties of complex nanoalloys. Of particular interest is the profound impact on the HOMO-LUMO gap of Au-20 - shrinking or growing depending on the location of a Pt doping. By considering different possible locations and morphologies for the introduced Pt, we identify alloying types which may have a greater probability of supporting collective plasma oscillations.