Isomers of smallPbnclusters(n=2–15): Geometric and electronic structures based onab initiomolecular dynamics simulatio

Abstract

The geometric and electronic structure of the Pb n clusters ͑n =2-15͒ has been calculated to elucidate its structural evolution and compared with other group-IV elemental clusters. The search for several low-lying isomers was carried out using the ab initio molecular dynamics simulations under the framework of the density functional theory formalism. The results suggest that unlike Si, Ge, and Sn clusters, which favor less compact prolate shape in the small size range, Pb clusters favor compact spherical structures consisting of fivefold or sixfold symmetries. The difference in the growth motif can be attributed to their bulk crystal structure, which is diamond-like for Si, Ge, and Sn but fcc for Pb. The relative stability of Pb n clusters is analyzed based on the calculated binding energies and second difference in energy. The results suggest that n = 4, 7, 10, and 13 clusters are more stable than their respective neighbors, reflecting good agreement with experimental observation. Based on the fragmentation pattern it is seen that small clusters up to n = 12 favor monomer evaporation, larger ones fragment into two stable daughter products. The experimental observation of large abundance for n = 7 and lowest abundance of n = 14 have been demonstrated from their fragmentation pattern. Finally a good agreement of our theoretical results with that of the experimental findings reported earlier implies accurate predictions of the ground state geometries of these clusters.

Aging effects on the nucleation of Pb nanoparticles in silica

“…18,19 These clusters are characterized by a small number of atoms ͑32 or less͒, and their high thermal stability is a result of the increase in their cohesive energy due to the formation of stiffer covalent bonds and the formation of specific topological arrangements that avoid dangling bonds. [18][19][20] Our results comprise silica embedded clusters which necessarily require the formation of atomic bonds with the surrounding matrix and, therefore, may not reproduce the same structures proposed for the free standing cases. However, the formation of similar covalent bonded clusters presenting fully coherent interfaces ͑i.e., without dangling bonds͒ with the silica matrix can result into a system with very low interface energy.…”

Photoelectron velocity-map imaging signature of structural evolution of silver-doped lead Zintl anions

“…[1][2][3][4] A large number of "ligand-free" Group 14 Zintl clusters have been prepared via the synthesis in the liquid phase or the laser vaporization in the gas phase, of which geometric and electronic structures have been explored experimentally and theoretically. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] In particular, the identifications of highly symmetric cage structures of the fascinating Pb 10 2− , Sn 12 2− , and Pb 12 2− clusters [10][11][12][13] intrigue and invite investigation of the metal-doped Zintl clusters [10][11][12] in the knowledge of whether a doped atom is endohedral or exohedral. Most of this work has involved the heavy Group 14 element species with the magic cluster size number of 10 and 12.…”

New Molecular Cage Clusters of Pb by Encapsulation of Mg

“…For Pb 12 , besides a deflection a significant broadening is also striking, that is, Pb 12 exhibits a permanent dipole moment and a structure deviating from an ideal icosahedron. [21] In contrast, the pickup of a single Mg atom results in profiles that are only deflected towards a high electric field. For Pb 17 only a deflection could be detected, but Mg 2 Pb 17 also displays a broadening, which points to an electric dipole moment.…”