Structure and bonding in quaternary AgAuPdPt clusters

Structural optimization of quaternary AgAuPdPt clusters up to 38 atoms is performed using adaptive immune optimization algorithm, and the Gupta many-body potential is adopted to model interatomic interaction. By fixing the atomic number of three types and varying the number of one type in quaternary clusters, geometrical effects by different types of noble metals are investigated. Results show that most configurations present the growth pattern based on the 19-atom double icosahedra, however, the structural transition model induced by increasing the number of the fourth noble atom is found to be different. Furthermore, the order parameter indicates that in quaternary clusters Ag and Au atoms mainly occupy the surface sites, Pd atoms tend to be in the middle shell, and the inner shell is located by Pt atoms. The study of the number of bonds indicates that Ag and Au atoms prefer scattering and forming a circle on the surface, respectively.