Half antiperovskites: V. Systematics in ordering and group-subgroup-relations for Pb2Pd3Se2, Bi2Pd3Se2, and Bi2Pd3S2

The crystal structures of Pb 2 Pd 3 Se 2 and superconducting Bi 2 Pd 3 Se 2 are investigated from single crystal X-ray diffraction. Thus, an enhanced view on structure trends can be given for the series Bi 2 M 3 Ch 2 and Pb 2 M 3 Ch 2 (M = Ni, Rh, Pd, Ch = S, Se) including structure-property relations to superconducting parkerite, Bi 2 Ni 3 S 2 , non superconducting Bi 2 Pd 3 S 2 , and trigonal shandite, Pb 2 Ni 3 S 2 . Systematics and deviations of the structure types are pointed out by group-subgroup relations from a common aristotype perovskite superstructure. Found structures and atomic site occupations are differenciated by means of Barnighausen trees, M site ordering, coordination spheres, and polyhedra sharing [Ch 2 A 4 ] as proposed by the scheme of ordered half antiperovskites A 2 M 3 Ch 2 = AM 3/2 Ch (A = In, Sn, Tl, Pb, Bi; M = Co, Ni, Rh, Pd, and Ch = S, Se). Low dimensional partial structures with short M—M distances are analyzed with respect to the occurrence of superconductivity in parkerites.