Density functional study of small bimetallic Ag-Pd clusters

The geometric and electronic properties of small AgmPdn clusters with m + n = 2-5 are studied within the framework of density functional theory in conjunction with two hybrid and one GGA exchange-correlation functional. For every composition, the global minimum is identified by using geometry optimization for a collection of initial structures. Results indicate that, for bimetallic tetramers and pentamers, the clusters shift from two-dimensional to three-dimensional structures with the addition of a second Pd atom. Ag2Pd2 is identified as the most stable tetramer by the calculation of the excess energy and second energy difference of bimetallic clusters. Concerning the fragmentation channels it is seen that the most favourable route in the majority of cases is via the evaporation of a single atom. Density of states calculations reveal that the increase of Pd content depletes the isolated s states close to the Fermi level, while at the same time shifts the d states to higher energies.