Halbantiperowskite: Zur Struktur der Shandite M 3/2 AS (M = Co, Ni; A = In, Sn) und ihren Typ‐Antitypbeziehungen

Half‐Antiperovskites: Structure and Type‐Antitype Relations of Shandites M 3/2 AS (M = Co, Ni; A = In, Sn) The crystallographic and electronic structures of the ternary shandite type sulfides M 3 A 2 S 2 (M = Co, Ni; A = In, Sn) were investigated by X‐ray diffraction, as well as density functional theory (DFT) band structure calculations with respect to superstructure and type‐antitype relations. The crystal structure of Ni 3 In 2 S 2 (space group $R{\bar 3}{\rm m}$ , a = 5.371Å, c = 13.563Å) was determined from a single crystal. The shandites show type‐antitype relations to oxostannates(II) M 2 Sn 2 O 3 (M = K, Rb) analogously to perovskite and antiperovskite. With a perovskite superstructure a group‐subgroup relation is given to antiperowskites like Ni 3 MgC. Because of the ordered occupation of half of the M‐positions the title compounds are described as half‐antiperowskites M 3/2 AS. The occupation scheme causes the formation of Kagomé‐nets. From bond distances covalent Ni–S bonds (< 2.20Å), ionic Sn–S and In–S‐interactions, as well as metallic In–Ni and Sn–Ni are concluded. The electronic band structures of the shandites show metallic characteristics similar to Ni 3 MgC. A band filling scheme explains the stability and properties from Co 3 In 2 S 2 to Ni 3 Sn 2 S 2 . The highest partly occupied bands are formed by a strong mixing of Co(Ni)‐3d, In(Sn)‐5p and S‐3p states. A bonding description [M 3 S 2 ] n− [A 2 ] n+ accounts for the structural and electronic properties. Band gaps for Ni 3 In 2 S 2 and Co 3 Sn 2 S 2 indicate metal– insulator and magnetic phase transitions.