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Zusammenfassung:
Two atomic arrangements were found near the equiatomic composition in
the strontium-lithium-arsenic system. Orthorhombic o-SrLiAs was
synthesized by reaction of elemental components at 950 degrees C,
followed by annealing at 800 degrees C and subsequent quenching in
water. The hexagonal modification h-SrLi1-xAs was obtained from
annealing of o-SrLiAs at 550 degrees C in dynamic vacuum. The structures
of both phases were determined by single-crystal X-ray diffraction:
o-SrLiAs, structure type TiNiSi, space group Pnma, Pearson symbol oP12,
a = 7.6458(2) angstrom, b = 4.5158(1) angstrom, c = 8.0403(3) angstrom,
V = 277.61(2) angstrom(3), R-F = 0.028 for 558 reflections; h-SrLi1-xAs,
structure type ZrBeSi, space group P6(3)/mmc, Pearson symbol hP6, a =
4.49277(9) angstrom, c = 8.0970(3) angstrom, V = 141.54(1) angstrom(3),
R-F = 0.026 for 113 reflections. The analysis of the electron density
within the framework of the quantum theory of atoms in molecules
revealed a charge transfer according to the (Sr1.3+Li0.8+As2.1), in
agreement with the electronegativities of the individual elements. The
electron localizability indicator distribution indicated the formation
of a 3D anionic framework [LiAs] in o-SrLiAs and a rather 2D anionic
framework [LiAs] in h-SrLi1-xAs. Magnetic susceptibility measurements
point to a diamagnetic character of both phases, which verifies the
calculated electronic density of states.
