Abstract: NBO,vibrational spectrum,aromatic characteristics and polarizability of ground state PtIr_n^0,±(n=1~5)clusters are analyzed by using density functional theory(b31yp).It shows that platinum atom gains charges during cluster growth,while some iridium atoms gain charges and others lose.They are transferred to platinum atom and other iridium atoms.More vibration peaks appear in IR and Raman sDectrums as more atoms are added. Vibration peaks of IR and Raman spectrum of Ptlr₄^- cluster are the strongest. PtIrl₃、Ptlr₅、PtIr₅⁺ clusters are aromatic.Bond interactions between atoms present a rising tendency with the increase of atomic number-Electronic structures of PtIr₃、Ptlrs₅⁺ clusters are relatively unstable, and delocalization effects are strong. With the increase of atomic number,stability of electronic structure of anionic clusters presents a rising tendency,and delocalization effect decreases gradually.

Key words: PtIr_n^0,±(n=1~5)clusters, electronic strueture, spectrum properties, density functional theory