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Onset of metallic behavior in magnesium clusters
Owen C Thomas1, Weijun Zheng, Shoujun Xu
1Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Physical Review Letters
|November 22, 2002
Summary
The study observed magnesium cluster anions transition to metallic behavior at n=18, indicated by closing s-p band gaps. Electronic shell structure influences this metallic transition, shown by gap reopenings and magic numbers.
Area of Science:
- Physical Chemistry
- Materials Science
- Quantum Chemistry
Background:
- Understanding the transition from atomic to bulk properties in metal clusters is crucial.
- Magnesium cluster anions (Mg-n) offer a model system to study electronic structure and metallic behavior.
Purpose of the Study:
- To investigate the electronic properties of magnesium cluster anions (Mg-n) across a range of sizes (n=3-35).
- To identify the size-dependent transition to metallic behavior in these clusters.
- To explore the role of electronic shell structure in governing cluster properties.
Main Methods:
- Photoelectron spectroscopy was used to measure the electronic states of mass-selected magnesium cluster anions.
- Analysis of s-p band gaps and their evolution with cluster size (n).
- Identification of mass spectral "magic numbers" and spectral features indicative of electronic shell closures.
Main Results:
- The s-p band gap in Mg-n clusters was observed to close at n=18, signifying the onset of metallic properties.
- Evidence for electronic shell structure was found through "reopenings" of the band gap at specific cluster sizes.
- Mass spectral magic numbers correlated with these electronic shell effects.
Conclusions:
- Magnesium cluster anions exhibit a transition to metallic behavior around n=18 due to the closure of electronic shells.
- The observed phenomena highlight the importance of quantum size effects and electronic shell structure in determining the properties of metal clusters.