Atom Superposition and Electron Delocalization
Definition and meaning of Atom Superposition and Electron Delocalization in chemistry.
Atom superposition and electron delocalization (ASED) is a computational chemistry method that describes how electrons distribute across multiple atoms in molecules and on catalyst surfaces using quantum mechanical superposition principles to model electron density and predict molecular adsorption properties.
In more detail
ASED theory combines quantum mechanics, where particles can exist in superposed states, with the physical reality of electron delocalization in chemical systems. Developed primarily for catalysis research, the ASED-MO (molecular orbital) approach calculates properties of adsorbate molecules as functions of band shifts in metallic and ionic systems. This method has proven particularly useful for predicting how molecules bond to metal surfaces and understanding how that bonding affects molecular structure. ASED is especially valuable in describing catalytic reactions where electron distribution changes significantly during adsorption.
Key facts
| Field | Physical Chemistry |
|---|---|
| Acronym Expansion | ASED-MO (Atom Superposition and Electron Delocalization Molecular Orbital) |
| Primary Application | Catalysis and surface chemistry |
| Developer | Alfred B. Anderson (Case Western Reserve University) |
ASED theory successfully predicted that acetylene (C2H2) bonds more strongly to a fourfold site on Ni(100) surfaces than on Ni(111), with greater C-C bond lengthening occurring at the more reactive site, helping explain nickel catalyst selectivity.
Frequently asked questions
How does ASED differ from classical resonance theory?
While resonance structures use classical valence bond diagrams to show electron delocalization, ASED is a quantum mechanical computational method that quantitatively models electron density and predicts adsorption behavior on metal catalyst surfaces.
Why is quantum superposition important in ASED?
Quantum superposition allows electrons to exist in multiple orbital configurations simultaneously, which is essential for accurately describing electron delocalization across atoms in molecules bound to metal catalysts and predicting catalytic reactivity.