Orthorombic La2Ni2In form – A new intergrowth CsCl – and AlB2 – type slabs

The crystal structure of a new orthorhombic modification of o-La2Ni2In (space group Pbam, Pearson code oP20, a = 7.5840(9), b = 15.4891(13), c = 3.9154(4) إ, Z = 4) has been investigated by X-ray single crystal methods. The structure is closely related to the tetragonal La2Ni2In form (Mo2FeB2 type, space group P4/mbm). Both La2Ni2In forms together with the structure types Mn2AlB2, Cr3AlB4, Lu5Ni2In4 and Nd11Pd4In9 form a homologous series, which is described by the general formula Rm+nT2nXm, where m and n are the number of CsCl and AlB2 related slabs per unit cell. In o-La2Ni2In the CsCl and AlB2 slabs are intergrown in a 4:4 ratio in a new mode. The coordination polyhedra of the lanthanum atoms are pentagonal prisms with seven additional atoms, the indium atom is surrounded tetrahexahedrally and the nickel atoms are in the center of tri-caped trigonal prisms.