The Study Of Structural Properties Of Pd_n, Pt_n(n=2-57) Clusters By Using Genetic Algorithm

Clusters are composed by two to thousands of atoms,molecules or ions by physical or chemical binding energy. The global minimum structure properties of a cluster is no doubt the most important one to study their other chemical and physical behavior. In this paper, we use a tight-binding potential combined with Genetic Algorithm to perform a systematic study for the global minima of Pdn , Ptn(n=2-57) clusters.For palladium cluster during the size of n=2-57, we find there exists struc- tural competition during the icosahedron-like, quindecahedron-like and fcc-li- ke. The geometrical structure of Pd54 is icosahedron without the central atom , and its average bond-energy is higher than that of the Pd54 with C5v geometri- cal structure. Our results show that the bind-energy of Pdn(n=2-57) clusters in- crease with the cluster size increasing. The second difference of energies and the excess energy are utilized to characterize and analyze the structure of Pdn clusters. We have a solution that the magic number geometries of Pd clusters contain 13, 22,30,38,41,46 and 55 atoms. By analyzing the average coordina- tion number and the average nearest-neighbor distance of these clusters, we study their magic structures , and we claim that the magic structure is mainly determined by its geometrical structure .Compared the results of platinum and palladium clusters in the size of n=2-57, we get main conclusions as follow:. Most of their symmetric structures are similar. In this paper, we find there exists structural competition between the icosahedron-like and the fcc-like. Both platinum and palladium clusters obviously take on the icosahedral gro- wth model. For the Pdn,Ptn(n=2-37) clusters ,we also find there exists struc- tures competition between the icosahedron-like and the quindecahedron-like. The average bind- energy of platinum and palladium clusters increase with n, and the average bind-energy of Ptn(n=2-57) clusters are higher than the corres- ponding palladium cluster bind-energy clearly. Pdn and Ptn(n=2-57) clusters have the same magic numbers in the range of n=2-40:n= 13,22,30 and 38, but for n≥41, they have clearly different magic numbers : the magic number geo- metries of Pd clusters are 41,46 and 55,and the magic number geometries of Pt clusters are 48 and 54.