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On the Chemical Bonding in LaPdIn 2 , LaNiMg 2 , and LaNiCd 2 ‐ Intermetallic Compounds with a Filled Distorted Variant of the CaIn 2 Type
Author(s) -
Doğan Ahmet,
Johrendt Dirk,
Pöttgen Rainer
Publication year - 2005
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200400389
Subject(s) - intermetallic , crystallography , substructure , cadmium , nickel , crystal structure , materials science , lanthanum , tantalum , metal , single crystal , chemistry , inorganic chemistry , metallurgy , alloy , structural engineering , engineering
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.