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Abstract

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.