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Intermetallics contribute significantly to our current demand for high-performance functional materials. However, understanding their chemistry is still an open and debated topic, especially for complex compounds such as approximants and quasicrystals. In this work, targeted topological data mining succeeded in (i) selecting all known Mackay-type approximants, (ii) uncovering the most important geometrical and chemical factors involved in their formation, and (iii) guiding the experimental work to obtain a new binary Sc–Pd 1/1 approximant for icosahedral quasicrystals containing the desired cluster. Single-crystal X-ray diffraction data analysis supplemented by electron density reconstruction using the maximum entropy method, showed fine structural peculiarities, that is, smeared electron densities in correspondence to some crystallographic sites. These characteristics have been studied through a comprehensive density functional theory modeling based on the combination of point defects such as vacancies a...

The new intermetallic compound Eu2Pd2Sn 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 Ca2Pd2Ge 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 μeff = 7.87 μB, close to the free ion Eu2+ value (μeff = 7.94 μB). The maximum of χ(T) at TN ∼ 13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat CP(T) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at TN a scenario of a transition to an incommensurate antiferromagnetic phase below TN followed by a commensurate configuration below 10 K is suggested., A new intermetallic compound, Eu2Pd2Sn, is so far the only rare-earth representative of the Ca2Pd2Ge structure type. Synthesis and characterization of the structure, together with magnetic properties, are discussed.

The two La2Pd3Ge5 and Nd2Pd3Ge5 compounds, crystallizing in the oI40-U2Co3Ge5 crystal structure, were targeted for analysis of their chemical bonding and physical properties. The compounds of interest were obtained by arc melting and characterized by differential thermal analysis, scanning electron microscopy, and X-ray diffraction both on powder and on a single crystal (for the La analogue), to ensure the high quality of the samples and accurate crystallographic data. Chemical bonding was studied by analyzing the electronic structure and effective QTAIM charges of La2Pd3Ge5. A significant charge transfer mainly occurs from La to Pd so that Ge species assume tiny negative charges. This result, together with the -(I)COHP analysis, suggests that, in addition to the expected homopolar Ge bonds within zigzag chains, heteropolar interactions between Ge and the surrounding La and Pd occur with multicenter character. Covalent La–Pd interactions increase the complexity of chemical bonding, which could not be adequately described by the simplified, formally obeyed, Zintl–Klemm scheme. Electric resistivity, specific heat, magnetization, and magnetic susceptibility as a function of temperature indicate for both compounds a metallic-like behavior. For Nd2Pd3Ge5, two low-temperature phase transitions are detected, leading to an antiferromagnetic ground state., The chemical bonding and physical properties of the two isotypic R2Pd3Ge5 (R = La and Nd) intermetallics are presented. La2Pd3Ge5 shows polar Ge−Pd/La multicenter interactions in addition to covalent Ge−Ge bonds. The bonding scenario is further complicated by the fact that Pd and La are also covalently interacting. For Nd2Pd3Ge5, an antiferromagnetic ground state is established after a long-range magnetic ordering (at ∼7.5 K) followed by a spin-reorientation transition (at ∼6.2 K).

The two La2Pd3Ge5 and Nd2Pd3Ge5 compounds, crystallizing in the oI40-U2Co3Ge5 crystal structure, were targeted for analysis of their chemical bonding and physical properties. The compounds of interest were obtained by arc melting and characterized by differential thermal analysis, scanning electron microscopy, and X-ray diffraction both on powder and on a single crystal (for the La analogue), to ensure the high quality of the samples and accurate crystallographic data. Chemical bonding was studied by analyzing the electronic structure and effective QTAIM charges of La2Pd3Ge5. A significant charge transfer mainly occurs from La to Pd so that Ge species assume tiny negative charges. This result, together with the -(I)COHP analysis, suggests that, in addition to the expected homopolar Ge bonds within zigzag chains, heteropolar interactions between Ge and the surrounding La and Pd occur with multicenter character. Covalent La-Pd interactions increase the complexity of chemical bonding, which could not be adequately described by the simplified, formally obeyed, Zintl-Klemm scheme. Electric resistivity, specific heat, magnetization, and magnetic susceptibility as a function of temperature indicate for both compounds a metallic-like behavior. For Nd2Pd3Ge5, two low-temperature phase transitions are detected, leading to an antiferromagnetic ground state.

The Sc2Ru compound, obtained by high-temperature synthesis, was found to crystallize in a new trigonal hP45 structure type [space group P3̅m1; a = 9.3583(9) Å and c = 11.285(1) Å]: Ru@Sc8 cubes, Ru@Sc12 icosahedra, and uncommon Ru@Sc10 sphenocoronae are the building blocks of a unique motif tiling the whole crystal space. According to density functional theory studies, Sc2Ru is a metallic compound characterized by multicenter interactions: a significant charge transfer occurs from Sc to Ru, indicating an unexpectedly strong ionic character of the interactions between the two transition metals. Energy calculations support our experimental results in terms of stability of this compound, contributing to the recurrent discussion on the limits of the high-throughput first-principles calculations for metallic materials design., A strong metal (Sc) to metal (Ru) charge transfer occurs for the new Sc2Ru compound, indicating a significant ionic contribution to the bond. The Sc2Ru trigonal crystal structure features a unique structural motif built up by Ru-centered simple cubes and icosahedra connected through hybrid sphenocorona polyhedra. This investigation represents also a little food for thought on the interplay between the experiments and theoretical prediction in metallic materials design.

The new intermetallic compound Eu2Pd2Sn 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 Ca2Pd2Ge 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 μeff = 7.87 μB, close to the free ion Eu2+ value (μeff = 7.94 μB). The maximum of χ(T) at TN ∼ 13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat CP(T) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at TN a scenario of a transition to an incommensurate antiferromagnetic phase below TN followed by a commensurate configuration below 10 K is suggested.

The 500 °C isothermal section of the La–Mg–Sn ternary system was established by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS) and powder X-ray diffraction (XRPD) on more than fifty alloys synthesized by induction melting and annealed. A few boundary binary compounds were found to dissolve the third element, forming ternary solid solutions, among which La(MgxSn1−x)3 (0≤x≤0.14, cP4-AuCu3) is the most extended. The existence and crystal structure of three ternary compounds were confirmed, and their homogeneity ranges at 500 °C determined: La3Mg4−xSn2+x (0.12≤x≤0.40, hP9-Zr3Cu4Si2), LaMg3−xSn2 (0.33≤x≤0.78, hP34-LaMg3−xGe2) and LaMgSn (oP12-TiNiSi). The crystal structures of two novel ternary stoichiometric compounds, found during this work, were determined from powder X-ray diffraction pattern analysis and refined using the Rietveld method: La6Mg23Sn ( F m 3 ¯ m , cF120-Zr6Zn23Si, a =1.47107(1) nm) and LaMgSn2 ( I 4 ¯ 2 m , tI32-LaMgSn2, a =0.83325(3) nm, c =1.24385(5) nm). The latter is the first representative of a new structure type and can be presented as composed by a complex Mg-Sn network hosting the bigger La atoms.

We present a machine learning approach for evaluating thermodynamic properties within model compositional/configurational spaces (CCSs) of complex intermetallics with Mackay-type building units. Recently, by performing high-throughput density functional theory calculations, we determine and analyze the formation energies for the recently synthesized 1/1 approximant of icosahedral quasicrystals in the Sc-Pd system possessing structural disorder. Here, sequentially increasing training sets are used in regression models based on compositional and topological descriptors for predicting formation enthalpies. We investigate different learning strategies. The obtained R2 dependencies show higher learning rates for the models using real features (composition and contact counters of defects) with small training set sizes, whereas using categorical features (topological types of defect structure fragments) result in a slightly higher prediction quality when the training set size increases. In connection with the obtained results, the proposed approach is considered as a tool for investigations of disordering phenomena in complex intermetallics as well as for a subsequent searching for new stable phases of Mackay-type approximants of quasicrystals.

The crystal structure of the new Er6Zn23Ge intermetallic compound was established by X-ray diffraction analysis on a twinned crystal (space group Fm3̅m, Wyckoff sequence: f2edba, cF120–Zr6Zn23Si, a =12.7726(6) Å). The crystal is composed of two nearly equal size domains, whose mutual orientation is described by a 180° rotation around the cubic [111] axis, i.e. a spinel-type twinning law, not common for intermetallics. Applying the nanocluster approach, Er6Ge octahedra and centered two-shell Zn45 clusters were found as structural building blocks, filling the crystal space in a NaCl-like arrangement. This description was adopted to interpret the twinning in terms of stacking faults in the fcc cubic close packed arrangement. Moreover, the assembly of the nanocluster units is proposed as a possible mechanism for crystal growth and twin formation, in agreement with the principle of the interface energy minimization. Experimental conditions such as supersaturation and co-formation of other phases are also considered as favorable factors for Er6Zn23Ge twin formation.

In this study, two novel Lu5Pd4Ge8 and Lu3Pd4Ge4 polar intermetallics were prepared by direct synthesis of pure constituents. Their crystal structures were determined by single crystal X-ray diffraction analysis: Lu5Pd4Ge8 is monoclinic, P21/m, mP34, a = 5.7406(3), b = 13.7087(7), c = 8.3423(4) Å, β = 107.8(1), Z = 2; Lu3Pd4Ge4 is orthorhombic, Immm, oI22, a = 4.1368(3), b = 6.9192(5), c = 13.8229(9) Å, Z = 2. The Lu5Pd4Ge8 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 and showing a metallic-like behavior. Gathered results for Lu5Pd4Ge8 and Lu3Pd4Ge4 permit to described both of them as composed by [Pd–Ge]δ– three 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 fragment i.e., Ge dumbbells as well as unique cis-Ge4 units. A comparative analysis of molecular orbital diagrams for Ge26– and cis-Ge10– anions 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.

The R2PdGe6 series (R = rare earth metal) was structurally characterized, and the results achieved were extended for a comprehensive study on R2MGe6 (M = another metal) compounds, employing symmetry-based structural rationalization and energy calculations. Directly synthesized R2PdGe6 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-Ce2(Ga0.1Ge0.9)7 as the correct structure. The alternative In-flux method, once optimized, produced three good quality R2PdGe6 single crystals: La2PdGe6 and Pr2PdGe6 turned out to be mS36-La2AlGe6-type non-merohedrally twinned crystals and Yb2PdGe6 is of oS72-Ce2(Ga0.1Ge0.9)7-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-SmNiGe3 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 R2PdGe6 (R = Y and La) in the three abovementioned structural models, and for La2MGe6 (M = Pt, Cu, Ag and Au) in the oS18 and oS72 modifications. The results indicate that the oS18-Ce2CuGe6 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.

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) A, wR 2 = 0.0306, 669 F 2 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 Barnighausen 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.

Synthesis and structural characterization of the two new lanthanum–magnesium–stannides La3Mg4−xSn2+x (0.12≤x≤0.40) and LaMg3−xSn2 (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La3Mg4−xSn2+x phase crystallizes in the hexagonal Zr3Cu4Si2 structure type (P6¯2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) A), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg3–xSn2 phase is the second representative of the trigonal LaMg3−xGe2 type, which is a superstructure of the LaLi3Sb2 structure type (P3¯1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) A). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg3−xSn2 off-stoichiometry from the geometrical point of view. Structural relationships between the La–Mg–Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB2-related compounds family and discussed with the aid of group-subgroup relations in the Barnighausen formalism.

The crystal structures of two new ternary phases, La{sub 4}Ag{sub 10}Mg{sub 3} and La{sub 4}Ag{sub 10.3}Mg{sub 12}, were refined from X-ray single crystal diffraction data. La{sub 4}Ag{sub 10}Mg{sub 3} crystallizes in the Ca{sub 4}Au{sub 10}In{sub 3} structure type, an ordered variant of the binary Zr{sub 7}Ni{sub 10} compound: orthorhombic, Cmce, oS68, a=14.173(5), b=10.266(3), c=10.354(3) A, Z=4, wR{sub 2}=0.0826, 676 F{sup 2} values, 50 variables. La{sub 4}Ag{sub 10.3}Mg{sub 12} represents a new structure type: orthorhombic, Cmmm, oS116-10.32, a=9.6130(3), b=24.9663(8), c=9.6333(2) A, Z=4, wR{sub 2}=0.0403, 1185 F{sup 2} values, 101 variables. The structural analysis of both compounds, highlighting a significant contraction of the Ag-Mg distances, suggests the existence of three-dimensional [Ag-Mg] networks hosting La atoms. LMTO calculations applied to La{sub 4}Ag{sub 10}Mg{sub 3} indicate that the strongest bonds occur for Ag-Ag and Ag-Mg interactions, and confirm the presence of a 3D{sub {infinity}}[Ag{sub 10}Mg{sub 3}]{sup {delta}}{sup -} polyanionic framework balanced by positively charged La atoms. -- Graphical abstract: An independent fragment of the 3D [Ag-Mg] framework in La{sub 4}Ag{sub 10}Mg{sub 3} together with an ELF section (1/2 0 0 basal plane). Display Omitted

Synthesis and characterization of about fifty alloys were performed in order to construct the isothermal section of the Y–Cu–Mg ternary system at 400 °C in the 0–66.7 at.% Cu concentration range. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS) and X-ray powder diffraction (XRPD) techniques were used to examine microstructures, identify phases and define their compositions and crystal structures. Phase equilibria in the investigated compositional region are characterized by the absence of extended ternary solid solutions and by the presence of at least ten ternary phases. Crystal structures of the previously reported Y 2 Cu 2 Mg, Y 5 Cu 5 Mg 8 , Y 5 Cu 5 Mg 13 , Y 5 Cu 5 Mg 16 and YCuMg 4 phases were confirmed. A ternary phase with homogeneity range around the YCu 4 Mg stoichiometry was found, crystallizing in the cF24--MgCu 4 Sn structure type; at 400 °C this phase coexists with a ternary solid solution based on the binary Laves phase Cu 2 Mg, which dissolves about 5 at.% Y. The equiatomic YCuMg phase was also found to exist: from the analysis of X-ray powder patterns it is suggested to crystallize in the hP9--ZrNiAl structure type ( a = 0.74449(4) nm, c = 0.39953(2) nm). Two other stoichiometric ternary phases were detected, of approximate compositions Y 25 Cu 18 Mg 57 and Y 13 Cu 9 Mg 78 , whose crystal structures are still unknown. In the Mg-rich region, a ternary phase forms characterized by a large homogeneity region.

The isothermal section of the La–Ni–Zn system at 400 °C was studied from 16.7 to 100 at.% La, by coupling X-ray powder diffraction and SEM–EDXS analyses on induction melted samples. Several binary phases were found to dissolve an appreciable amount of the third element forming ternary solid solutions which extend along lines at a constant La content. Particularly, a continuous solid solution was detected between the LaNi5 and LaZn5 isostructural compounds. Seven ternary phases were found to exist at 400 °C, both stoichiometric and showing homogeneity ranges at a constant La concentration. The crystal structures of LaNiZn (hP9-ZrNiAl), La2Ni2Zn (oI10-Pr2Ni2Al) and La3Ni3Zn (oS28-Y3Co3Ga) were confirmed; quite extended homogeneity ranges were detected for the last two phases. The crystal structure of the new phase of stoichiometry La7Ni2Zn was solved ab initio from X-ray powder diffraction data: it crystallizes in its own structure type, tetragonal, P4/mbm, tP20, a = 1.24104(9) nm, c = 0.38256(3) nm. A phase of general formula La(Ni,Zn)3 extends from about 2.5 to 9 at.% Zn whose crystal structure corresponds to the hexagonal CeNi3 type: a negligible addition of Zn is likely to stabilize this structure instead of the analogue rhombohedral PuNi3 type, which the binary compound LaNi3 crystallizes in. Two more ternary phases were found in the isothermal section at 400 °C: the stoichiometric ∼La3Ni4Zn3 and the LaNi1+xZn2−x (0

The crystal structures of the new ternary compounds LaCuMg4 and TbCuMg4 were studied by X-ray powder diffraction and single-crystal methods, respectively. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. LaCuMg4 crystallizes in the UCoAl4 structure type (space group P6¯2m, Pearson code hP18, a=1.03911(1), c=0.45126(1) nm, Z=3, RF=0.0654), while TbCuMg4 exhibits a new structure (space group Cmmm, Pearson code oS48, a=1.35797(6), b=2.03333(9), c=0.39149(2) nm, Z=8, wR2=0.0426). Both structures represent a family of two-layer compounds. All interatomic distances indicate metallic type bonding. The structural peculiarities of these compounds and their relations are discussed.

Single crystals of diterbium dinickel trimagnesium, Tb2Ni2Mg3, were synthesized from the elements by induction melting. The novel compound crystallizes in the space group Cmmm with one Mg atom of site symmetry mmm and the Tb, Ni and other Mg atom in m2m positions. This ternary compound represents a new structure type that is derived from Ru3Al2B2 by way of Wyckoff site distribution. The two-layer structure of Tb2Ni2Mg3 is a new representative of a homologous linear structure series of general formula R′k+nX2nR′′2m+k based on structural fragments of the α-Fe, CsCl and AlB2 structure types. The Tb atoms in the structure are enclosed in 17-vertex polyhedra, while rhombododeca­hedra and distorted rhombododeca­hedra surround the Mg atoms, and equatorially tricapped trigonal prisms form around the Ni atoms. All inter­atomic distances indicate metallic type bonding.

The isothermal section of the Ce–Cu–Zn phase diagram was constructed at 200 °C over the whole concentration range as a result of X-ray powder diffraction, wavelength dispersive spectrometry and electron probe microanalysis. The existence of one new ternary compound Ce2Cu5–5.7Zn2–1.3 was observed at this temperature and its crystal structure was refined from X-ray single crystal data (structure type Ce2Ni5Zn2, space group R 3 ¯ m , Pearson code hR18, a = 0.4998(1)–0.5078(1) nm, c = 3.6924(5)–3.6987(4) nm). The homogeneity regions were determined for a number of solid solutions on the basis of binary phases.

Investigations of the solid solution of CeCu 5− x Zn x composition (CaCu 5 structure type) are presented in this article. We refined the XPD patterns for the series of alloys of the CeCu 5 –CeZn 5 pseudobinary system. The crystal structure of this solid solution was determined by means of the single crystal and powder X-ray methods. Besides, the limit of the measured solid solution has been determined. WDS and EPMA were used for examining the number of phases and the phase content.

The limited solid solution CeCu6−xZnx, x=0÷0.84 (structure type CeCu6, space group Pnma, Pearson code oP28, a=0.8112(1)÷0.8154(2), b=0.5102(1)÷0.5056(1), c=1.0162(2)÷1.0185(2) nm) was observed in the Ce–Cu–Zn ternary system at 200 °C. The homogeneity range of the solid solution was investigated by X-ray powder diffraction, wavelength dispersive spectrometry (WDS) and electron probe microanalysis (EPMA). X-ray single crystal diffraction was used for the detailed refinement of the crystal structure of CeCu5.16Zn0.84.

The crystal structure of new RTZn 2 intermetallic compounds (R = La, Ce, Tb; T = Co, Cu) was determined. The X-ray diffraction data showed that these compounds are isostructural to the new ternary compound ErCuCd 2 , which was found to crystallize with a superstructure of the ErCd 3 structure type (space group Cmcm, Pearson code oS16, a = 0.7097(1) nm, b = 1.0659(3) nm, c = 0.4471(1) nm, V = 0.3382(2) nm 3 , Z = 4). The obtained reliability factors are R F = 0.0240 and R W = 0.1127 for 235 unique reflections (|F 0 | > 4.00σ|F 0 |).

The whole 500 °C isothermal section of the La–Mg–Ge ternary system was constructed. The existence and crystal structure of three ternary compounds were confirmed: La2+xMg1−xGe2 (τ2, P4/mbm, tP10–Mo2FeB2, 0≤x≤0.25), La4Mg5Ge6 (τ3, Cmc21, oS60–Gd4Zn5Ge6) and La4Mg7Ge6 (τ4, C2/m, mS34, own structure type). Five novel compounds were identified and structurally characterized: La11Mg2Ge7 (τ1, P42/ncm, tP88-8, own structure type, a=1.21338(5), c=1.57802(6) nm), LaMg3−xGe2 (τ5, P 3 ¯ 1c, hP34-0.44, own structure type, x=0.407(5), a=0.78408(4), c=1.45257(7) nm), La6Mg23Ge (τ6, Fm 3 ¯ m, cF120–Zr6Zn23Si, a=1.46694(6) nm), La4MgGe10−x (τ7, x=0.37(1), C2/m, mS60-1.46, own structure type, a=0.88403(8), b=0.86756(8), c=1.7709(2) nm, β=97.16°(1) and La2MgGe6 (τ8, Cmce, oS72–Ce2(Ga0.1Ge0.9)7, a=0.8989(2), b=0.8517(2), c=2.1064(3) nm). Disordering phenomena were revealed in several La–Mg–Ge phases in terms of partially occupied sites. The crystal structures of La11Mg2Ge7 and LaMg3−xGe2 are discussed in details. The latter is a √3a×√3a×2c superstructure of the LaLi3Sb2 structure type; the symmetry reduction scheme is shown in the Barnighausen formalism terms.

The structures of MgNi nanoparticles are searched for by a computational methodology combining atomistic modeling, global optimization searches and density-functional theory (DFT) calculations. Sizes of up to 45 atoms are considered for several different compositions. Core-shell structures are found in most cases. However, there are also exceptions, such as the three-shell high-symmetry matryoshka clusters Mg@Ni-12@Mg-32 (of anti-Mackay icosahedral geometry) and Mg@Ni-12@Mg-14 (of tetrahexahedral geometry). Other high-symmetry structures comprise the core-shell cubic Mg8Ni6, the tetrahexahedral cluster Mg14Ni13 and the pentadocahedral cluster Mg21Ni12. The results of the atomistic models are compared with DFT calculations, obtaining a good agreement.

International audience; The ternary intermetallic compound EuCu9Mg2 has been synthesized. The magnetic properties have been investigated by magnetization measurements and 151Eu Mössbauer spectroscopy. Europium is divalent and a spin freezing is observed at 25 K. However, this spin freezing is characterized by the onset of strong magnetic irreversibility, which suggests a cluster-glass freezing. The Mössbauer spectra can be analyzed as the superposition of two subspectra of Eu2+ ions, which is consistent with a cluster-glass freezing. A transition to the ferromagnetic state is induced by application of a magnetic field the order of 0.5 T. This anomalous feature is attributed to quantum spin fluctuations that oppose the long-range ferromagnetic ordering, due to the two-dimensional topology of the geometric arrangement of the Eu2+ ions. This 2D-topology is also evidenced by a quadratic variation of the specific heat as a function of temperature down to 2.7 K. The electrical resistivity is also analyzed in the framework of intermetallic compounds dominated by ferromagnetic spin fluctuations above the spin-freezing temperature.

Single crystals of the MgZn2Ce alloy (magnesium dizinc cerium) were synthesized by a two-step method which couples the thermal treatment of pressed pellets of the pure elements with subsequent arc melting. The compound crystallizes in a Heusler-type (MnCu2Al) structure in the space group Fm\overline{3}m, with one Zn site (site symmetry \overline{4}3m), one Ce and one Mg site (both with m\overline{3}m site symmetry). All inter­atomic distances indicate metallic type bonding.