A density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic aluminum phosphide clusters

► Carbon monoxide adsorbs on neutral and ionic aluminum phosphide clusters. ► The Al-top sites are the preferred one in the most chemisorptions sites. ► Adsorption energies decrease with cluster size for both neutral and ionic clusters. ► νCO in cationic complexes are larger than those in neutral and anion.