Structural and dynamic properties of the polyanionic hydrides SrAlGeH and BaAlGeH

• The quaternary aluminium hydrides SrAlGeH and BaAlGeH were synthesized from either hydrogenating the intermetallic AlB2-type precursors SrAlGe and BaAlGe or reacting SrH2 with a mixture of Al and Ge in the presence of pressurized hydrogen. Their structures were characterized by X-ray and neutron powder diffraction of the corresponding deuterides. The compounds crystallize with the trigonal SrAlSiH structure type (space group P3m1, Z = 1, a = 4.2435(2) and 4.3450(2) Å, c = 4.9710(3) and 5.2130(4) Å for SrAlGeH and BaAlGeH, respectively) and feature a two-dimensional polyanion [AlGeH]2− which represents a corrugated hexagon layer built from three-bonded Al and Ge atoms. H is terminally attached to Al. Polyanions [AlGeH]2− are electron precise and, according to electronic structure calculations, the quaternary hydrides display band gaps with sizes between 0.7 and 0.8 eV. Infrared and inelastic neutron scattering spectroscopy show Al–H stretching and bending mode frequencies at around 1250 and 870 cm−1, respectively. SrAlGeH and BaAlGeH are thermally stable up to at least 500 °C. When exposed to air the hydrides decompose rapidly to amorphous, orange colored materials.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Zintl phases

Main group metal hydrides

Superconductors

Semiconductors

Inorganic Chemistry

oorganisk kemi

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