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Inside powders: a theoretical model of interfaces between MgO nanocrystallites
Keith P McKenna1, Peter V Sushko, Alexander L Shluger
1Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK. k.mckenna@ucl.ac.uk
Journal of the American Chemical Society
|June 16, 2007
Summary
This study reveals how electrons and holes interact with magnesium oxide (MgO) nanocrystallite interfaces. Holes prefer trapping on surface anions, while electrons favor surface defects, impacting MgO optical properties.
Area of Science:
- Materials Science
- Quantum Chemistry
- Surface Science
Background:
- Understanding nanocrystallite interfaces is crucial for materials applications.
- Electron and hole trapping mechanisms influence material properties.
- Magnesium oxide (MgO) nanocrystallites have diverse potential applications.
Purpose of the Study:
- To investigate electron- and hole-trapping properties at MgO nanocrystallite interfaces.
- To explore the optical properties of MgO nanocrystallite interfaces.
- To provide a fundamental understanding of charge carrier behavior in MgO powders.
Main Methods:
- Utilized a quantum-mechanical embedded-cluster method.
- Employed time-dependent density functional theory (TD-DFT).
- Calculated optical absorption spectra.
Main Results:
- Delocalized holes can be transiently trapped within MgO powders.
- Holes preferentially trap on low-coordinated anions (O-) at nanocrystallite surfaces.
- Electrons trap at interfaces, particularly at surface kink and corner sites.
- Optical absorption spectra indicate excitation of buried features at < 5 eV.
Conclusions:
- Hole trapping is energetically favorable at surface anions (O-).
- Electron trapping is localized at specific interface defect sites.
- MgO nanocrystallites exhibit optical absorption features accessible at lower photon energies than commonly assumed.
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