Examinando por Materia "Cluster stability"

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    Structure, stability and bonding in the 1Au 10 clusters
    (ELSEVIER SCIENCE BV, 2012-06-29) David, Jorge; Guerra, Doris; Restrepo, Albeiro; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)
    A stochastic exploration of the quantum conformational space for the 1Au 10 system using a modified Metropolis acceptance test afforded 15 stable configurations in the MP2/SDDALL potential energy surface. The global minimum is predicted to be a 3D structure with D2 d symmetry. Topological analyses of the electron densities suggest that bonding appears to be of intermediate character, with substantial contributions from both covalent and closed shell interactions and that there is a direct correlation between the topological complexity of the electron density and cluster stability. Evidence regarding the nature of the interactions is gathered from many sources, including the total number of delocalized electrons (nde), a novel covalency index. Localization indices and condensed Fukui functions predict higher electron populations on peripheral, lowly coordinated atoms. © 2012 Elsevier B.V. All rights reserved.
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    Structures, energies, and bonding in the water heptamer
    (AMER INST PHYSICS, 2013-07-28) Acelas, Nancy; Hincapie, Gina; Guerra, Doris; David, Jorge; Restrepo, Albeiro; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)
    In this paper we report the geometries and properties of 38 distinct geometrical motifs located on the B3LYP/6-31+G(d), MP2/6-311++G(d, p) potential energy surfaces of the water heptamer. Binding energies of up to 45 kcal/mol are calculated. All motifs fall within 10 kcal/mol of the most stable conformation, with at least 13 structural patterns located no more than 3 kcal/mol above, leading to a very complex potential energy surface, populated by a multitude of motifs each one allowing large numbers of conformations. Cluster stability does not seem to be correlated with the number of hydrogen bonds. Compact structures are energetically favored by electronic energies with zero-point energy corrections, while more open structures are preferred when temperature and entropy are accounted for. The molecular interactions holding the clusters as discrete units lead to large binding energies but are not strong enough to cause significant changes in the geometries of the interacting monomers. Our results indicate that bonding in the water heptamers can be considered as largely non-shared interactions with contributions from intermediate character of increasing covalency. © 2013 AIP Publishing LLC.