Syntheses and Structures of the Germanides CaNiGe and MgCoGe as well as Chemical Bonding in CaNiGe and CaNi₂Ge₂

Abstract

The intermetallic germanides CaNiGe and MgCoGe have been synthesized from the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffractions both on powders and single crystals: CeFeSi structure type, P4/nmm, a = 4.19341(3), c = 6.6264(1) Å, wR2 = 0.030, 124 F2 values, 10 variable parameters for CaNiGe and a = 3.8960(4), b = 6.1929(11) Å, wR2 = 0.048, 104 F2 values, 10 variable parameters for MgCoGe. In CaNiGe and MgCoGe the transition metal and germanium atoms build [TGe] layers (T = Ni, Co), which are separated by the calcium and magnesium atoms, respectively. The crystal structures of CaNiGe and MgCoGe as well as chemical bonding in CaNiGe and CaNi2Ge2 are discussed in terms of LMTO bond structure calculation and analysis using the Electron Localization Function (ELF). The Ge–Ge bond formation in polyanionic $^{3}_{\infty}\rm [NiGe]^{-}$ network of CaNi2Ge2 can formally be regarded as oxidative coupling product of $^{2}_{\infty}\rm [NiGe]^{2-}$ layers of CaNiGe.

Complex Intermetallic Compounds: CaNi5Ge3, Ca15Ni68Ge37, and Ca7Ni49Ge22 – Three Multifaceted Ni‐Ge Framework Structures Combining the Structural Motifs of Ni3Ge and CaNi2Ge2

“…At slightly lower values, namely, below η = 0.55, four monosynaptic basins that are associated with Ge2/Ge3 are observed (Figure 8, b). This is in good agreement with the ELF calculated for the Ge-Ge bond in CaNi 2 Ge 2 , [24] which has very similar characteristics. At values below η = 0.49, two monosynaptic basins at opposite sites of Ge1 are observed (Figure 8, c), which merge at lower ELF values.…”

“…In the course of our investigations of the Ca/Ni/Ge system several ternary compounds, which contain two-dimensional Ni-Ge layers (CaNiGe, Ca 4 Ni 4 Ge 3 , Ca 2 Ni 3 Ge 2 ) [22][23][24] as well as three-dimensional Ni-Ge networks (CaNi 2 Ge 2 , CaNiGe 3 , CaNiGe 2 ) [25][26][27] , have been characterized. Further research led to the discovery of the title compounds CaNi 5 Ge 3 , Ca 15 Ni 68 Ge 37 , and Ca 7 Ni 48.9(4) Ge 22.1 (4) , each of which crystallized in a new structure type.…”

Spin-glass-like behavior of CaNi1−xMnxGe

“…For instance, the combination of Ca with TmGe (Tm = Mn, Ni) crystallizes respectively in the 111 and 122 type compounds of CaTmGe and CaT m 2 Ge 2 . [15][16][17] For these two compounds the Mn sublattice are both AFM ordered for intralayer Mn ions, 15,17 which verifies again the metric rule based on in-plane Mn-Mn distances. In comparison the Ni-based compounds are both confirmed to be PPM.…”

“…This result is consistent with the fact that the compounds of CaTmGe (Tm: Fe, Co, and Cu) do not exist, whereas the compound CaMnGe has the same CeFeSi-type structure as CaNiGe, and their lattice parameters are close to each other. 15,16 The Mn-doped CaNiGe samples exhibit metallic luster and pieces of metallic sheets usually cleave from the bulk, implying that the samples possess a layered crystal structure. Figure 2 shows XRD patterns of CaNi 1-x Mn x Ge with x between 0 and 1.…”

BiOCuS: A new superconducting compound with oxypnictide-related structure

“…Many compounds of metals with appropriate anions crystallize with the same structure as these new superconductors. For example, CaNiGe [4] and NaAlSi [5] are isostructural to LiFeAs. The second one is a superconductor (T c = 7 K).…”