Lowest energy states of small Pd clusters using density functional theory and standard ab initio methods. A route to understanding metallic nanoprobes

Ab initio and density functional theory calculations were performed on smal l Pd clusters to assess their precise energy level characteristics. The gro und states of Pd and Pd-3 are found to be singlets while Pd-2 and Pd-4 are triplets. Pd-2 is found to be a weak dimer with bond energy of 18 kcal/mol. The trimer is triangular and the tetramer is of tetrahedral geometry. A no nadditive effect can be observed as the size of cluster increases. Larger c lusters are bonded better than smaller ones. The second lowest state of Pd- 4 is a singlet of tetrahedral geometry. Modern DFT methods yield results of better quality than sophisticated standard ab initio methods, thereby prov iding an affordable avenue for the analysis of larger clusters and potentia l nanoelectronics probes.