Lowest Energy States of Small Pd Clusters Using Density Functional Theory and Standard ab Initio Methods. A Route to Understanding Metallic Nanoprobes

Abstract

Ab initio and density functional theory calculations were performed on small Pd clusters to assess their precise energy level characteristics. The ground 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 nonadditive effect can be observed as the size of cluster increases. Larger clusters 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 providing an affordable avenue for the analysis of larger clusters and potential nanoelectronics probes.

DFT Study of Small Palladium Clusters Pdn and Their Interaction with a CO Ligand (n = 1–9)

“…In his ground state, the palladium atom presents a closed-shell electronic configuration 4d 10 ( 1 S). In order to make stable Pd-Pd bonds, the contribution of the 5s orbital to the electronic density is required.…”

“…10-x 5s x electronic configuration (0 Յ x Յ 1), which can be justified from a perturbation viewpoint by the mixture of 4d 10 and 4d 9 5s 1 states. A computation shows that the latter triplet electronic configuration lies 19.8 kcal/mol above the ground state, which remains relatively close to the experimental value of 21.6 kcal/mol.…”

“…Another question to be raised concerns the spin multiplicity. Because the palladium atom presents a closed-shell electronic configuration (4d 10 ), part of its 4d electronic density must necessarily be promoted into the nearest orbitals, in this case 5s, to enable the formation of a stable metal-metal bond. Consequently, all structures have been optimized for the various accessible spin multiples, i.e.…”

Structural properties of nanoclusters: Energetic, thermodynamic, and kinetic effects

“…In this size range they compared several 1D, 2D and 3D isomers; moreover, they considered a few selected structures at N = 19 and 55. Their results indicate that the lowest-lying isomers are 3D already starting for the tetramer (Moseler et al, 2001;Zacarias et al, 1999), and that Ih structures are favored over both Dh and CO structures for N = 13 and 55. These results are in good agreement with previous calculations by Kumar and Kawazoe (2002).…”

Effect of Molecular Structure and Hydration on the Uptake of Gas-Phase Sulfuric Acid by Charged Clusters/Ultrafine Particles

“…DFT becomes a proper tool for precise and accurate ab initio computation (Zacarias et al 1999). In the present study we have employed the PW91 method, which has been proposed by Perdew and Wang (1992) and includes both the exchange correction and correlation parts.…”