On the Chemical Bonding in LaPdIn 2 , LaNiMg 2 , and LaNiCd 2 ‐ Intermetallic Compounds with a Filled Distorted Variant of the CaIn 2 Type

The new intermetallic compound LaNiCd 2 was prepared by induction melting of the elements in a sealed tantalum tube in a water‐cooled sample chamber. LaNiCd 2 was characterized by X‐ray powder and single crystal data: MgCuAl 2 type, Cmcm , a = 427.2(2), b = 994.8(4), c = 816.5(4) pm, w R 2 = 0.0429, 302 F 2 values, 17 parameters. Refinement of the occupancy parameters revealed small nickel defects resulting in the composition LaNi 0.958(6) Cd 2 for the investigated crystal. The structure may be described as a nickel filled LaCd 2 substructure with distorted CaIn 2 related arrangement. The cadmium substructure (304‐324 pm Cd‐Cd) resembles the lonsdaleite type. Together the nickel and cadmium atoms build up a three‐dimensional [NiCd 2 ] network (277 and 278 pm Ni‐Cd) in which the lanthanum atoms fill distorted pentagonal channels. The COHP analysis reveals a Cd‐Cd ICOHP bonding energy comparable with cadmium metal. We show by comparison of Cd‐Cd bonds in LaNiCd 2 with those in LaCd 2 and hypothetical La□Cd 2 that Cd‐Cd bonding is significantly weakened by the formation of the strong Ni‐Cd bonds. Higher electron counts, as in LaPdIn 2 , lead to stronger Pd‐In bonds at the expense of the In‐In bonding.