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

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., doeecahedron 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 Pt-21 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 Ptn (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 electronic property and geometry was also discussed. (C) 2009 Published by Elsevier B.V.