Solid State Syntheses and Structure of LaPdCd₂ and PrNi_0.951(4)Cd₂

The intermetallic cadmium compounds LaPdCd₂ and PrNi_0.951(4)Cd₂ were synthesized from the elements in sealed tantalum tubes in an induction furnace. Both phases were investigated by X-ray diffraction on powders and single crystals: MgCuAl₂-type, Cmcm, Z = 4, a = 431.9(1), b = 1015.7(4), c = 835.7(2) pm, wR2 = 0.0436, 326 F² values, 16 variables for LaPdCd₂ and a = 420.26(8), b = 981.0(2), c = 815.3(1) pm, wR2 = 0.0404, 604 F₂ values, 17 variables for PrNi_0.951(4)Cd₂. A small nickel deficit was observed for the PrNi_0.951(4)Cd₂ crystal. The cadmium atoms build up orthorhombically distorted three-dimensional networks (Cd-Cd distances: 302 - 334 pm) that resemble the structure of hexagonal diamond, lonsdaleite. Together with the palladium (nickel) atoms, [PdCd2] and [Ni_0.951(4)Cd₂] networks are formed which leave distorted hexagonal channels for the rare earth atoms.