1. Bond hybridization in Au alloys: Extracting structural information from the x-ray-absorption white line
- Author
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R. Manaila, D. Macovei, I. Adil-Smith, Marian Manciu, and B. R. Orton
- Subjects
Electronegativity ,symbols.namesake ,Crystallography ,Materials science ,Transition metal ,Chemical bond ,Fermi level ,symbols ,Intermetallic ,Electronic structure ,Atomic physics ,Antibonding molecular orbital ,Spectral line - Abstract
Au L3 x-ray-absorption near-edge spectra were measured with synchrotron radiation on a series of Au-X compounds, with X5Ga, In, Ge, and Sn. The white-line feature of the spectra, as a rough measure of charge transfer upon compound formation, was related to the local composition around the Au atoms. This enabled us to estimate the local Au environment, in cases where its knowledge is missing. Chemical bonding in intermetallic compounds of transition metals ( T) with less electronegative elements ( X) in the same d row or in groups III-IV-V of the periodic table has stimulated intense theoretical and experimental work. A valence-electron charge-transfer mechanism, initially proposed by Pauling for CuAl 2 , 1 was subsequently developed 2 to explain the chemical interaction between the metallic components. It emphasizes a non-d-character charge being transferred onto the T atoms, as an effect of their higher electronegativity, compensated by a back transfer of d charge off T, preserving its charge neutrality. Such a mechanism is equivalent to T-X hybridization, 3 with antibonding T(d)X( sp ) states upshifted above the Fermi level ( EF), corresponding to the T(d) and X( sp ) states ‘‘emptied’’ by the d-non-d charge transfer. Spectroscopic techniques like x-ray-absorption, x-ray emission, and photoemission were used to probe the electronic structure on both sides of EF and give an experimental evidence of the bonding effects. 4 A large series of T12xXx (T5Au,Pt,Ir,Re,Ag,Pd; X5Al,Ga,In,Si,Ge,Sn! com more...
- Published
- 1996
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