Halbantiperowskite II: zur Kristallstruktur des Pd3Bi2S2

Halfantiperovskites II: on the Crystal Structure of Pd₃Bi₂S₂ 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 M_3/2AS (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]^δ? networks as proposed for Sn₂O₃]^2? and Hg₃S₂]²⁺.