Localization of an excess electron in sodium halide clusters

Honea, Eric C.; Homer, M. L.; Labastie, P.; Whetten, Robert L.

doi:10.1103/physrevlett.63.394

Cited by 137 publications

(69 citation statements)

References 21 publications

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“…Alkali-halide clusters make for another good case study of ionic-bonded heterogeneous clusters [17][18][19]. The results appear different from those described here.…”

Section: Sodium Vapor With H 2 O Moleculescontrasting

confidence: 83%

Comparison of reactive nucleation of silver and alkali clusters in the presence of oxygen and water

Bréchignac

Cahuzac

Leygnier

et al. 1999

The European Physical Journal D

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The nucleation of silver-atom vapor in the presence of O 2 and H 2 O molecules has been investigated by photoionization mass spectrometry and compared to the case of alkali-atom vapor. Relative intensities in mass spectra show that silver vapor does not react with H 2 O molecules, in contrast with sodium vapor. When O 2 and H 2 O are simultaneously present, hydroxided products are observed. Results emphasize the role of stable units, (NaOH) 2 or (KOH) 2 , for alkalies, and more complex hydrated or hydroxided systems, involving trimers, for silver. Similarities are found with water dissociative adsorption on an oxygen-predosed silver surface.

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“…Alkali-halide clusters make for another good case study of ionic-bonded heterogeneous clusters [17][18][19]. The results appear different from those described here.…”

Section: Sodium Vapor With H 2 O Moleculescontrasting

confidence: 83%

Comparison of reactive nucleation of silver and alkali clusters in the presence of oxygen and water

Bréchignac

Cahuzac

Leygnier

et al. 1999

The European Physical Journal D

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“…In contrast to the work on metalrich ionic clusters Cs 2n+z O n [4] and Na n+z Cl n [5] where the surplus of electrons, which are not involved in ionic bonds, were found to be delocalized in spherical shells if z is larger than n, the one excess electron system Na n Cl n−1 shows that the excess electron released can form an F center-like localized state [6,7]. These results have suggested that a transition from localized to delocalized electrons must occur at some intermediate excess metal concentration.…”

Section: Pacsmentioning

confidence: 70%

Loss of metallicity in metal rich lithium oxide clusters

Bréchignac

Cahuzac

Frutos

et al. 1997

Z Phys D - Atoms, Molecules and Clusters

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Mixed lithium-lithium oxide aggregates are experimentally obtained from unimolecular evaporative cascades starting at metal rich Li + p (Li 2 O) n species and ending with the stoichiometric limit Li + (Li 2 O) n , for several sizes of the oxide part (Li 2 O) n with 0 ≤ n ≤ 8. The results show evidence of the vanishing of the properties of the quantum metallic droplet i.e. shell closing and odd-even alternation, portrayed in the dissociation energy, with increasing size of the oxide component. The competition between monomer and dimer lithium evaporation from the heated metal rich Li + p (Li 2 O) n species points out the influence of the perturbation induced by the oxide component on the mixed metal oxide clusters. 36.40; 82.30; 82.65 Heterogeneous two component materials consisting of units which are respectively metallic and insulating in bulk, exhibit different properties with variation of the metal concentration. In the low metal concentration limit, theoretical and experimental studies showed that the excess of valence electrons gives rise to F-center like localized states [1]. At higher concentration a non-metal to metal transition takes place associated with an electronic delocalization. Such a transition occurs in metal molten salt solution at excess metal atom concentration of 0.1-0.2 [2]. PACS:As Landman pointed out, the "metallization of ionic clusters" opens a new dimension for investigations of excess electron delocalization [3]. In contrast to the work on metalrich ionic clusters Cs 2n+z O n [4] and Na n+z Cl n [5] where the surplus of electrons, which are not involved in ionic bonds, were found to be delocalized in spherical shells if z is larger than n, the one excess electron system Na n Cl n−1 shows that the excess electron released can form an F center-like localized state [6,7]. These results have suggested that a transition from localized to delocalized electrons must occur at some intermediate excess metal concentration. Actually in the intermediate case of Na 14 Cl 14−x with 1 ≤ x ≤ 6, molecular dynamics simulations reveal that the excess electrons are of a more delocalized nature than that of the other valence electrons in the cluster leading to segregation of the metallic component at a face of the ionic cluster [3,8]. From these calculations, the transition from F-center localized state to metallic behavior should occur in alkali halide clusters at excess metal atom concentration similar to the one observed in bulk matter [8].Such a transition from "non metallic to metallic" behavior of the excess electrons must also take place in metalmetal oxide systems. However both experimental and theoretical data available for metal-rich oxide clusters are in the earliest phase, so far [4, 9].In this paper we present the evolution of the properties of metal-rich Li + p (Li 2 O) n clusters portrayed in their stabilities as a function of oxide concentration. For a given number p of lithium atoms the collective properties of the p − 1 excess electrons i.e. shell closing and odd-even effects graduall...

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“…Is it localized on a certain part of the cluster, or is it delocalized on all Na ÷ centers? Honea et al [7] have measured abundancies and electronic properties of Na,F,_ ~ clusters. They put in evidence that the behavior of these molecules is largely dominated by the presence of an excess electron.…”

Section: Introductionmentioning

confidence: 99%

Ab-initio study of localization of an excess electron in sodium halide clusters

Giraud-Girard

Maynau

1992

Z Phys D - Atoms, Molecules and Clusters

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Abstract. The equilibrium geometries of Nan F, and Na,,F,,_ 1 are optimized for n =2, 3, 4 at the SCF level. The Na, F, molecules appear as formed by Na + and F ions. The paper studies the localization of the excess electron in the Na, F,_ 1 molecules. Na~F,_I is obtained by removing from Na, F, a fluorine atom, and the excess electron takes the place of this lacking center, and allows a weak bond between the neighbouring Na atoms. Secondary minimum geometries, for which the excess electron has no defined place, are also studied. PACS: 31.20.Di; 31.20.Ej; 31.90.+s; 36.40.+d lattice. Na14X13 is the smallest cluster corresponding to these conditions; (ii) in class II, a cluster Na,X, would form a cuboid structure, and Na,X,,_ 1 has the same structure but presents a vacancy corresponding to a lacking X center. The experimental studies strongly suggest that the excess electron localizes on this vacancy, when it exists. One of the proofs is that the excess electron is weakly bound in class I, and strongly bound in class II compounds, where a localized site is available.In this work, Na,F,_ ~ clusters of class II are studied using ab-initio techniques. The preceeding hypothesis on the localization of excess electron is tested for n = 2, 3, 4.

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Localization of an excess electron in sodium halide clusters

Cited by 137 publications

References 21 publications

Comparison of reactive nucleation of silver and alkali clusters in the presence of oxygen and water

Comparison of reactive nucleation of silver and alkali clusters in the presence of oxygen and water

Loss of metallicity in metal rich lithium oxide clusters

Ab-initio study of localization of an excess electron in sodium halide clusters

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