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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 33, Number 1
BKCSDE 33(1)
January 20, 2012 

Electronic and Bonding Properties of BaGaGeH: Hydrogen-induced Metal-insulator Transition from the AlB2-type BaGaGe Precursor
Dae-Bok Kang
Metal hydride, Zintl phase, Electronic structure
The hydrogenation of AlB2-type BaGaGe exhibits a metal to insulator (MI) transition, inducing a puckering distortion of the original hexagonal [GaGe] layers. We investigate the electronic structure changes associated with the hydrogen-induced MI transition, using extended Hückel tight-binding band calculations. The results indicate that hydrogen incorporation in the precursor BaGaGe is characterized by an antibonding interaction of π on GaGe with hydrogen 1s and the second-order mixing of the singly occupied antibonding π * orbital into it, through Ga-H bond formation. As a result, the fully occupied bonding π band in BaGaGe changes to a weakly dispersive band with Ge pz (lone pair) character in the hydride, which becomes located just below the Fermi level. The Ga-Ge bonds within a layered polyanion are slightly weakened by hydrogen incorporation. A rationale for this is given.
153 - 158
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