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 Pd6clusters, 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.