Density functional theory study on CO adsorption on the PdnAl (n = 1–5) clusters

Abstract

The configurations, stability, electronic properties and CO adsorption of the ground state Pd[Formula: see text]Al (n = 1–5) clusters are calculated by the density functional theory (DFT). The results reveal that the lowest-energy configurations of Pd[Formula: see text]Al clusters inherit the geometries of the host Pd[Formula: see text] clusters to a larger extent. The C atom in CO molecule prefers to approach more Pd atoms rather than Al atoms in small Pd[Formula: see text]Al clusters. Pd[Formula: see text]AlCO clusters have higher average binding energies than the corresponding small Pd[Formula: see text]CO clusters except for PdCO. AlCO and Pd3AlCO clusters possess better kinetic stability than their neighbors by the HOMO–LUMO gaps. Except for Pd6 clusters, CO molecule prefers to adsorb on small Pd[Formula: see text] clusters rather than Pd[Formula: see text]Al clusters. Both the Al–Pd bonding in Pd[Formula: see text]Al clusters and C–Pd bonding in Pd[Formula: see text]AlCO clusters have certain covalent characters.