Local, Gradient-Corrected, and Hybrid Density Functional Calculations on Pdn Clusters for n = 1−6

Full optimizations of Pd n cluster geometries have been performed using density functional methods and allowing the occurrence of low-symmetry structures. To account for at least partially for relativistic effects, use was made of Hay and Wadt RECP. The following ground states were found respectively for n = 1, 2, 3, 4, and 6: 1 S (4 d 10 ), 3 B 2 { C 2 v }, 3 B 2 { C 2 v }, 3 B 2 g { D 4 h }. Various exchange-correlation functionals have been tested on Pd 2 and Pd 3, including the recent B3LYP one. The introduction of some exact exchange reduces significantly the predicted binding energy, which thus matches the experimental values in the case of Pd 2 . Moreover, it allows us to overcome the serious SCF convergence problems arising from the presence in these clusters of a large number of low-lying, nearly degenerate states.