A comparative chemical bonding analysis for the germanides La2MGe6 (M=Li, Mg, Al, Zn, Cu, Ag, Pd) and Y2PdGe6 is presented, together with the crystal structure determination for M=Li, Mg, Cu, Ag. The studied compounds adopt the two closely related structure types oS72‐Ce2(Ga0.1Ge0.9)7 and mS36‐La2AlGe6, containing zigzag chains and corrugated layers of Ge atoms bridged by M species, with La/Y atoms located in the biggest cavities. Chemical bonding was studied by means of the quantum chemical position‐space techniques QTAIM (quantum theory of atoms in molecules), ELI‐D (electron localizability indicator), and their basin intersections. The new penultimate shell correction (PSC0) method was introduced to adapt the ELI‐D valence electron count to that expected from the periodic table of the elements. It plays a decisive role to balance the Ge−La polar‐covalent interactions against the Ge−M ones. In spite of covalently bonded Ge partial structures formally obeying the Zintl electron count for M=Mg2+, Zn2+, all the compounds reveal noticeable deviations from the conceptual 8−N picture due to significant polar‐covalent interactions of Ge with La and M ≠ Li, Mg atoms. For M=Li, Mg a formulation as a germanolanthanate M[La2Ge6] is appropriate. Moreover, the relative Laplacian of ELI‐D was discovered to reveal a chemically useful fine structure of the ELI‐D distribution being related to polyatomic bonding features. With the aid of this new tool, a consistent picture of La/Y−M interactions for the title compounds was extracted.

Direct synthesis and structural characterization of a series of polar rare earth palladium germanides of R2Pd3Ge5 composition (R = La–Nd, Sm) is reported. The crystal structure of the Nd representative was determined by single-crystal X-ray diffraction analysis (U2Co3Si5-type, SG: Ibam, oI40, Z = 4, a = 10.1410(6), b = 12.0542(8), c = 6.1318(4) Å, wR2 = 0.0306, 669 F2 values, 31 variables). The crystal structures of the other homologues were ensured by powder X-ray diffraction pattern analysis. A smooth variation of the cell dimensions is observed through the rare earth series. The structure of the studied compounds can be interpreted as consisting of a complex three-dimensional [Pd3Ge5]δ− network spaced by the rare earth cations. Within the concept of symmetry reduction, a Bärnighausen tree is used to rationalize the related crystal structures of the RPd2Ge2, RPdGe3 and R2Pd3Ge5 ternary compounds, enriching the large family of the BaAl4 derivatives. Moreover, syntheses with metal fluxes were performed, some of which were successful to obtain large crystals of La2Pd3Ge5 (using Bi as solvent) and Nd2Pd3Ge5 (using Pb as solvent) stoichiometry

The new intermetallic compound Eu 2 Pd 2 Sn has been investigated. A single crystal was selected from the alloy and was analyzed by single-crystal X-ray diffraction, revealing that this compound possesses the noncentrosymmetric Ca 2 Pd 2 Ge structure type being, so far, the only rare-earth-based representative. Bonding analysis, performed on the basis of DOS and (I)COHP, reveals the presence of strong covalent Sn–Pd bonds in addition to linear and equidistant Pd–Pd chains. The incomplete ionization of Eu leads to its participation in weaker covalent interactions. The magnetic effective moment, extracted from the magnetic susceptibility χ(T) is μ eff = 7.87 μ B , close to the free ion Eu 2+ value ( μ eff = 7.94 μ B ). The maximum of χ(T) at T N ∼ 13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat C P ( T ) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at T N a scenario of a transition to an incommensurate antiferromagnetic phase below T N followed by a commensurate configuration below 10 K is suggested.

The RPdGe series (R = rare earth metal) was structurally characterized, and the results achieved were extended for a comprehensive study on RMGe (M = another metal) compounds, employing symmetry-based structural rationalization and energy calculations. Directly synthesized RPdGe exists for almost all R-components (R = Y, La-Nd, Sm and Gd-Lu) and even if with La is probably metastable. Several single crystal X-ray analyses (R = Y, Ce, Pr, Nd, Er and Lu) indicated oS72-Ce(GaGe) as the correct structure. The alternative In-flux method, once optimized, produced three good quality RPdGe single crystals: LaPdGe and PrPdGe turned out to be mS36-LaAlGe-type non-merohedrally twinned crystals and YbPdGe is of oS72-Ce(GaGe)-type. The vacancy ordering phenomenon was considered as a possible cause of the symmetry reduction relations connecting the most frequently reported 2 : 1 : 6 structural models (oS18, oS72 and mS36) with the oS20-SmNiGe aristotype. The detected twin formation is consistent with the symmetry relations, which are discussed even considering the validity of the different structural models. DFT total energy calculations were performed for RPdGe (R = Y and La) in the three abovementioned structural models, and for LaMGe (M = Pt, Cu, Ag and Au) in the oS18 and oS72 modifications. The results indicate that the oS18-CeCuGe structure, prevalently proposed in the literature, is associated with the highest energy and thus it is not likely to be realized in these series. The oS72 and mS36 polytypes are energetically equivalent, and small changes in the synthetic conditions could easily stabilize any of them, in agreement with experimental results obtained by direct and flux syntheses.

Gold intermetallic chemistry is very rich, covering different classes of compounds, which range from Hume-Rothery to Zintl phases to polar intermetallics to quasicrystals. Au’s relativistic effects are frequently mentioned as...

In this study, two novel Lu 5 Pd 4 Ge 8 and Lu 3 Pd 4 Ge 4 polar intermetallics were prepared by direct synthesis of pure constituents. Their crystal structures were determined by single crystal X-ray diffraction analysis: Lu 5 Pd 4 Ge 8 is monoclinic, P2 1 /m, mP34, a = 5.7406(3), b = 13.7087(7), c = 8.3423(4) Å, β = 107.8(1), Z = 2; Lu 3 Pd 4 Ge 4 is orthorhombic, Immm, oI22, a = 4.1368(3), b = 6.9192(5), c = 13.8229(9) Å, Z = 2. The Lu 5 Pd 4 Ge 8 analysed crystal is one more example of non-merohedral twinning among the rare earth containing germanides. Chemical bonding DFT studies were conducted for these polar intermetallics with a metallic-like behavior. Gathered results for Lu 5 Pd 4 Ge 8 and Lu 3 Pd 4 Ge 4 permit to described both of them as composed by [Pd-Ge] δthree dimensional networks bonded to positively charged lutetium species. From the structural chemical point of view, the studied compounds manifest some similarities to the Zintl phases, containing well-known covalent fragments i.e., Ge dumbbells as well as unique cis-Ge 4 units. A comparative analysis of molecular orbital diagrams for Ge 2 6and cis-Ge 10anions with COHP results supports the idea of the existence of complex Pd-Ge polyanions hosting covalently bonded partially polarised Ge units. The palladium atoms have an anion like behaviour and being the most electronegative cause the noticeable variation of Ge species charges from site to site. Lutetium charges oscillate around +1.5 for all crystallographic positions. Obtained results explained why the classical Zintl-Klemm concept can't be applied for the studied polar intermetallics.It is interesting to remark that the ternary RE-Pd-Ge compounds manifest a tendency to be stoichiometric with ordered distributions of constituents through distinct Wyckoff sites. Moreover, within Pd-Ge fragments, both species have small coordination numbers (usually four or five) with very similar topological distributions of neighbours (tetrahedral coordination or its derivatives). These features may be considered as geometrical traces of a similar chemical role of Pd and Ge. That is why symmetry reduction from certain aristotypes can conveniently depict the distortions related with an ordered distribution of atom sorts. Such analysis has been conducted in the literature for AlB 2 derivative polymorphs of REPdGe [8] and BaAl 4 derivatives of the RE 2 Pd 3 Ge 5 [7,9] family of compounds. In systems where such types of relationships exist, the geometric factor is surely of great importance. Thus, varying RE, different polymorphs [8] or even novel compounds may form. As an example, heavy rare earth containing RE 5 Pd 4 Ge 8 (RE = Er, Tm) [4] and RE 3 Pd 4 Ge 4 (RE = Ho, Tm, Yb) [3] series of compounds may be cited.During exploratory syntheses conducted in the Lu-Pd-Ge system in the framework of our ongoing studies on Ge-rich ternary compounds, the Lu representatives of the abovementioned 5:4:8 and 3:4:4 stoichiometries were detected for the first time. In this paper, results on the synthesis and structural charac...

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The monogermanide LuGe is obtained via high‐pressure high‐temperature synthesis (5–15 GPa, 1023–1423 K). The crystal structure is solved from single‐crystal X‐ray diffraction data (structure type FeB, space group Pnma, a=7.660(2) Å, b=3.875(1) Å, and c=5.715(2) Å, RF=0.036 for 206 symmetry independent reflections). The analysis of chemical bonding applying quantum‐chemical techniques in position space was performed. It revealed—beside the expected 2c‐Ge‐Ge bonds in the germanium polyanion—rather unexpected four‐atomic bonds between lutetium atoms indicating the formation of a polycation by the excess electrons in the system Lu3+(2b)Ge2−×1 e−. Despite the reduced VEC of 3.5, lutetium monogermanide is following the extended 8‐N rule with the trend to form lutetium‐lutetium bonds utilizing the electrons left after satisfying the bonding needs in the anionic Ge‐Ge zigzag chain.