- Cubic Fluorite-Type CaH2 with a Small Bandgap
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A cubic variant of CaH2 adopting a fluorite-type crystal structure was synthesized by cationic substitution with La or Y, yielding the first alkaline earth hydride-based with fluorite-type framework. The material has a bandgap of ~2.5 eV (greenish yellow in color), which is much smaller than that of orthorhombic PbCl2-type CaH2 (4.4 eV) and is, in fact, the smallest among alkaline or alkaline earth metal hydrides reported to date. Analysis of the density functional theory band structure of cubic-CaH2 indicates that its conduction band minimum is formed mainly by the interaction between the Ca 3d eg orbitals around the crystallographic cavity defined by cubes of H- ions. The use of such cavities in the creation of low-lying conduction band minima by semiconductors is extremely rare, and has similarities to inorganic electrides.
- Mizoguchi, Hiroshi,Park, Sangwon,Honda, Takashi,Ikeda, Kazutaka,Otomo, Toshiya,Hosono, Hideo
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supporting information
p. 11317 - 11320
(2017/08/30)
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- Homoleptic tetrahydrometalate anions MH4-(M = Sc, Y, La). Matrix infrared spectra and DFT calculations
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Laser-ablated Sc, Y, and La atoms react with molecular hydrogen upon condensation in excess argon, neon, and deuterium to produce the metal dihydride molecules and dihydrogen complexes MH2 and (H2)MH2. The homoleptic tetrahydrometalate anions ScH4-, YH4-, and LaH4- are formed by electron capture and identified by isotopic substitution (D2, HD, and H2 + D2 mixtures). Doping with CCl4 to serve as an electron trap virtually eliminates the anion bands, and further supports the anion identifications. The observed vibrational frequencies are in agreement with the results of density functional theory calculations, which predict electron affinities in the 2.8-2.4 eV range for the (H2)ScH2, (H2)YH2, and (H2)LaH2 complexes, and indicate high stability for the MH4- (M = Sc, La, Y) anions and suggest the promise of synthesis on a larger scale for use as reducing agents.
- Wang, Xuefeng,Andrews, Lester
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p. 7610 - 7613
(2007/10/03)
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