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Title: Probing the Electronic Structure of Early Transition-Metal Oxide Clusters:  Polyhedral Cages of (V 2 O 5 ) n - ( n = 2-4) and (M 2 O 5 ) 2 - (M = Nb, Ta)

Abstract

Vanadium oxide clusters, (V 2O 5)n, have been predicted to possess interesting polyhedral cage structures, which may serve as ideal molecular models for oxide surfaces and catalysts. Here we examine the electronic properties of these oxide clusters via anion photoelectron spectroscopy for (V 2O 5)n - (n = 2-4), as well as for the 4d/5d species, Nb 4O 10 - and Ta 4O 10 -. Wellresolved photoelectron spectra have been obtained at 193 and 157 nm and used to compare with density functional calculations. Very high electron affinities and large HOMO-LUMO gaps are observed for all the (V 2O 5)n clusters. The HOMO-LUMO gaps of (V 2O 5)n, all exceeding that of the band gap of the bulk oxide, are found to increase with cluster size from n = 2-4. For the M4O10 clusters, we find that the Nb/Ta species yield similar spectra, both possessing lower electron affinities and larger HOMO-LUMO gaps relative to V 4O 10. The structures of the anionic and neutral clusters are optimized; the calculated electron binding energies and excitation spectra for the global minimum cage structures are in good agreement with the experiment. Evidence is also observed for the predicted trend of electron delocalization versusmore » localization in the (V 2O 5)n - clusters. Further insights are provided pertaining to the potential chemical reactivities of the oxide clusters and properties of the bulk oxides.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
985079
Report Number(s):
PNNL-SA-56862
Journal ID: ISSN 0002-7863; 2010; KC0301020; TRN: US201016%%1763
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 129; Journal Issue: 43
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANIONS; CATALYSTS; ELECTRONIC STRUCTURE; ELECTRONS; EXCITATION; FUNCTIONALS; MOLECULAR MODELS; OXIDES; PHOTOELECTRON SPECTROSCOPY; SPECTRA; TRANSITION ELEMENTS; VANADIUM OXIDES; Environmental Molecular Sciences Laboratory

Citation Formats

Zhai, Hua-Jin, Döbler, Jens, Sauer, Joachim, and Wang, Lai-Sheng. Probing the Electronic Structure of Early Transition-Metal Oxide Clusters:  Polyhedral Cages of (V 2 O 5 ) n - ( n = 2-4) and (M 2 O 5 ) 2 - (M = Nb, Ta). United States: N. p., 2007. Web. doi:10.1021/ja0750874.
Zhai, Hua-Jin, Döbler, Jens, Sauer, Joachim, & Wang, Lai-Sheng. Probing the Electronic Structure of Early Transition-Metal Oxide Clusters:  Polyhedral Cages of (V 2 O 5 ) n - ( n = 2-4) and (M 2 O 5 ) 2 - (M = Nb, Ta). United States. doi:10.1021/ja0750874.
Zhai, Hua-Jin, Döbler, Jens, Sauer, Joachim, and Wang, Lai-Sheng. Mon . "Probing the Electronic Structure of Early Transition-Metal Oxide Clusters:  Polyhedral Cages of (V 2 O 5 ) n - ( n = 2-4) and (M 2 O 5 ) 2 - (M = Nb, Ta)". United States. doi:10.1021/ja0750874.
@article{osti_985079,
title = {Probing the Electronic Structure of Early Transition-Metal Oxide Clusters:  Polyhedral Cages of (V 2 O 5 ) n - ( n = 2-4) and (M 2 O 5 ) 2 - (M = Nb, Ta)},
author = {Zhai, Hua-Jin and Döbler, Jens and Sauer, Joachim and Wang, Lai-Sheng},
abstractNote = {Vanadium oxide clusters, (V2O5)n, have been predicted to possess interesting polyhedral cage structures, which may serve as ideal molecular models for oxide surfaces and catalysts. Here we examine the electronic properties of these oxide clusters via anion photoelectron spectroscopy for (V2O5)n - (n = 2-4), as well as for the 4d/5d species, Nb4O10 - and Ta4O10 -. Wellresolved photoelectron spectra have been obtained at 193 and 157 nm and used to compare with density functional calculations. Very high electron affinities and large HOMO-LUMO gaps are observed for all the (V2O5)n clusters. The HOMO-LUMO gaps of (V2O5)n, all exceeding that of the band gap of the bulk oxide, are found to increase with cluster size from n = 2-4. For the M4O10 clusters, we find that the Nb/Ta species yield similar spectra, both possessing lower electron affinities and larger HOMO-LUMO gaps relative to V4O10. The structures of the anionic and neutral clusters are optimized; the calculated electron binding energies and excitation spectra for the global minimum cage structures are in good agreement with the experiment. Evidence is also observed for the predicted trend of electron delocalization versus localization in the (V2O5)n - clusters. Further insights are provided pertaining to the potential chemical reactivities of the oxide clusters and properties of the bulk oxides.},
doi = {10.1021/ja0750874},
journal = {Journal of the American Chemical Society},
number = 43,
volume = 129,
place = {United States},
year = {Mon Oct 01 00:00:00 EDT 2007},
month = {Mon Oct 01 00:00:00 EDT 2007}
}