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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 24, Number 3
BKCSDE 24(3)
March 20, 2003 

Electronic Structure and Bonding in the Ternary Silicide YNiSi3
Gi-Hong Sung, Dae-Bok Kang
Band structure, Bonding, Silicide
An analysis of the electronic structure and bonding in the ternary silicide YNiSi3 is made, using extended Huckel tight-binding calculations. The YNiSi3 structure consists of Ni-capped Si2 dimer layers and Si zigzag chains. Significant bonding interactions are present between the silicon atoms in the structure. The oxidation state formalism of (Y3+)(Ni0)(Si3)3- for YNiSi3 constitutes a good starting point to describe its electronic structure. Si atoms receive electrons from the most electropositive Y in YNiSi3, and Ni 3d and Si 3p states dominate below the Fermi level. There is an interesting electron balance between the two Si and Ni sublattices. Since the p* orbitals in the Si chain and the Ni d and s block levels are almost completely occupied, the charge balance for YNiSi3 can be rewritten as (Y3+)(Ni2-)(Si2-)(Si-Si)+, making the Si2 layers oxidized. These results suggest that the Si zigzag chain contains single bonds and the Si2 double layer possesses single bonds within a dimer with a partial double bond character. Strong Si-Si and Ni-Si bonding interactions are important for giving stability to the structure, while essentially no metal-metal bonding exists at all. The 2D metallic behavior of this compound is due to the Si-Si interaction leading to dispersion of the several Si2 p bands crossing the Fermi level in the plane perpendicular to the crystallographic b axis.
325 - 333
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