Density functional theory study of Aun (n = 1–5) clusters supported on montmorillonite

Authors

  • Claudia Briones-Jurado,

    Corresponding author
    1. Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Av. 1 de Mayo S/N, Cuautitlán Izcalli, CP 54740, Edo. México, México
    • Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Av. 1 de Mayo S/N, Cuautitlán Izcalli, CP 54740, Edo. México, México
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  • Pablo de la Mora,

    1. Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México, Av. Universidad 3000 Circuito Exterior S/N, CP 04510 Ciudad Universitaria, Ciudad de México, México
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  • Esther Agacino-Valdés

    1. Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Av. 1 de Mayo S/N, Cuautitlán Izcalli, CP 54740, Edo. México, México
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Abstract

The adsorption and nucleation of gold clusters Aun (n = 1–5) on montmorillonite (MMT) is studied using the density functional theory. All the calculations were performed using the full-potential linearized augmented-plane-wave method as implemented in the WIEN2k code. We constructed a MMT supercell of formula Si16Al6Mg2O40(OH)8 containing four unit cells and the first moments of the nucleation process were studied by adding the gold atoms one by one on the MMT. The results show that the interaction energies between the gold clusters and the MMT are negative indicating that the Aun–MMT complexes are stable. In the Aun–MMT systems (n = 3–5), two gold atoms maintain the coordination with basal oxygens and the Au[BOND]O distance was about 2.0–2.3 Å. The Au[BOND]Au average distance is 2.6 Å in the supported gold clusters. The formation of the second layer of gold atoms occurs upon the arrival of the third gold atom. We are reporting that the transition of 2D → 3D gold cluster structures is located from Au3 to Au4 on MMT. The total density of states of clusters Au, Au2, Au3, Au4, and Au5 on MMT allows us to affirm that (i) gold atoms are the main contributors to the states closest to the Fermi level and (ii) in Au4–MMT and Au5–MMT systems, the main contributors to the states closest to the Fermi level are the most external gold atoms, and therefore these atoms are probably the most susceptible to interact with adsorbates and the most active sites. Odd–even oscillations in the values of the energy gap and interaction energy were found: the odd-numbered supported clusters, Au3 and Au5, have larger energy gaps and more negative interaction energies. © 2012 Wiley Periodicals, Inc.

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