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Synthesis, Structure and Chemical Bonding of CaCo 2 Si 2 and BaCo 2 Ge 2 – Two New Compounds with ThCr 2 Si 2 Structure Type
Author(s) -
Siggelkow Lisa,
Hlukhyy Viktor,
Fässler Thomas F.
Publication year - 2010
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.200900533
Subject(s) - intermetallic , crystallography , crystal structure , chemistry , chemical bond , electron localization function , covalent bond , superconductivity , electron , condensed matter physics , physics , organic chemistry , alloy , quantum mechanics
The intermetallic compounds CaCo 2 Si 2 and BaCo 2 Ge 2 were prepared by melting mixtures of the elements in an arc‐furnace under argon. Single crystals were obtained by special heat treatment in welded tantalum ampoules. The compounds were investigated by powder and single‐crystal X‐ray diffraction. Both title compounds crystallize in the ThCr 2 Si 2 structure type with space group I 4/ mmm : a = 3.9161(3) Å, c = 9.9184(7) Å, wR2 = 0.032, 220 F 2 values, 9 variable parameters for CaCo 2 Si 2 ; a = 4.0859(3) Å, c = 11.779(2) Å, wR2 = 0.046, 106 F 2 values, 9 variable parameters for BaCo 2 Ge 2 . The described intermetallic compounds demonstrate the tunable distance between the tetrel elements, which is often observed for compounds with ThCr 2 Si 2 structure type. In CaCo 2 Si 2 a covalent Si–Si bond is present, whereas no Ge–Ge bond occurs in BaCo 2 Ge 2 . The CaCo 2 Si 2 and BaCo 2 Ge 2 are isoelectronic to BaFe 2 As 2 , the parent compound of a new “122” family of high temperature superconductors. The crystal chemistry and chemical bonding in title compounds is discussed in terms of LMTO band structure calculations and a topological analysis using the Electron Localization Function (ELF).