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Schlagwörter:
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Zusammenfassung:
A new crystalline form of BaGe5 was obtained at a pressure of 15(2) GPa
in the temperature range from 1000(100) to 1200(120) K. Single-crystal
electron and powder X-ray diffraction patterns indicate a body-centered
orthorhombic structure (space group Imma, Pearson notation oI24) with
unit cell parameters a = 8.3421(8) angstrom, b = 4.8728(5) angstrom, and
c = 13.7202(9) angstrom. The crystal structure of hp-BaGe5 consists of
four-bonded Ge atoms forming complex layers with Ge-Ge contacts between
2.560(6) and 2.684(3) angstrom; the Ba atoms are coordinated by 15 Ge
neighbors in the range from 3.341(6) to 3.739(4) angstrom. Analysis of
the chemical bonding using quantum chemical techniques in real space
reveal charge transfer from the Ba cations to the anionic Ge species. Ge
atoms having nearly tetrahedral environments show an
electron-localizability-based oxidation number close to 0; the
four-bonded Ge atoms with a Psi-pyramidal environment adopt a value
close to 1-. In agreement with the calculated electronic density of
states, the compound is a metallic conductor (electrical resistivity of
ca. 240 mu O cm at 300 K), and magnetic susceptibility measurements
evidence diamagnetic behavior with chi(0) = -95 x 10(-6) emu mol(-1).
