Zusammenfassung
The crystallographic structure of Pd3Bi2S2 was determined from x-ray diffraction data and compared to parkerite (Ni3Bi2S2), shandite (Ni3Pb2S2), and a high pressure form of laflammeite (Pd3Pb2S2). For Pd3Bi2S2 the structure type of corderoite, Hg3S2Cl2 (I213) was found that represents a cubic variant (a = 8,3097(9) Å) of the parkerite structure. It turns out to be a structural antitype of the low ...
Zusammenfassung
The crystallographic structure of Pd3Bi2S2 was determined from x-ray diffraction data and compared to parkerite (Ni3Bi2S2), shandite (Ni3Pb2S2), and a high pressure form of laflammeite (Pd3Pb2S2). For Pd3Bi2S2 the structure type of corderoite, Hg3S2Cl2 (I213) was found that represents a cubic variant (a = 8,3097(9) Å) of the parkerite structure. It turns out to be a structural antitype of the low temperature cubic modification of K2Sn2O3, analogously to the previously investigated type-antitype relation of shandit to high-temperature K2Sn2O3. The crystal structures are derived from perovskites ABO3 and antiperovskites M3AX with only half of the O- and M-sites being occupied. The M = Ni, Pd site ordering in shandite and parkerite type compounds is discussed in terms of ordered half antiperovskite (HAP) structures M3/2AS (A = Bi, Pb). The electronic band structure of Pd3Bi2S2 is calculated within the framework of density functional theory. The compound is found to behave metallic while K2Sn2O3 and corderoite are semiconductors. The bonding is analysed in terms of covalently bond [Pd3S2]- networks as proposed for [Sn2O3]2- and [Hg3S2]2+.
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