Structures and structural evolution of Pt_n (n = 15-24) clusters with combined density functional and genetic algorithm methods

摘要

Low-lying structures and structural evolution of Pt_n (n = 15-24) clusters were studied using a genetic algorithm followed by local optimization with density functional theory calculations. As a whole, the lowest energy structures of Pt_n (n = 15-24) clusters are likely to form open structural motifs not the atomic closed shell structures. Four kinds of structural motifs, i.e., dodecahedron based (DODB), cuboc_tahedron based (COB), layered triangular (LT) and cubic configurations have been investigated for the medium-sized Pt_n (n = 15-24) clusters. The Pt_n (n = 15-16,19, 24) prefer the DODB growth pattern. While the Pt_n (n = 17-18, 20) lean to the LT configuration. The lowest energy structures of Ptz1 and Pt_23 clusters adopt the cubic structure. Pt_n clusters at n = 15, 18, 24 are relatively more stable and these clusters are "magic" numbered. Three different spin multiplicities (M= 1, 3 and 5) have been examined for Pt_n (n = 15-24) clusters, and found that the most stable Pt_22 cluster is the only one in triplet state. These results are significantly different from those predicted in earlier works. The relationship between elec_tronic property and geometry was also discussed.