Ternary plumbides ATPb2 (A = Ca, Sr, Ba, Eu; T = Rh, Pd, Pt) with distorted, lonsdaleite-related substructures of tetrahedrally connected lead atoms

The magnesium- and cadmium-rich intermetallic phases EuTMg2 (T = Rh, Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 were synthesized from the elements in sealed niobium or tantalum ampoules and with heat treatments in muffle or induction furnaces. The samples were characterized by powder X-ray diffraction and the structures were refined from single crystal X-ray diffractometer data. EuTMg2 (T = Pd, Ag, Pt, Au) and EuTCd2 (T = Pd, Pt, Au) crystallize with the MgCuAl2 type, space group Cmcm, while EuRhMg2, EuIrMg2 and CaRhMg2 adopt the YSiPd2 type, space group Pnma. The striking crystal chemical motif of both series of compounds are networks of puckered Mg(Cd) hexagons in ABAB stacking sequence that derive from the aristotype AlB2; however, with different tiling. Temperature dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements indicate stable divalent europium. Antiferromagnetic ordering sets in at 20.2 (EuIrMg2), 22.3 (EuPdMg2), 21.3 (EuAgMg2), 10.9 (EuPdCd2) and 15.5 K (EuPtCd2), respectively. The stable antiferromagnetic ground states are substantiated by metamagnetic transitions. The 151Eu isomer shifts show a linear correlation with the valence electron count for the whole series of EuTMg2, EuTCd2, EuTIn2 and EuTSn2 phases.

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EuTMg₂ (T = Pd, Ag, Ir, Pt, Au), EuTCd₂ (T = Pd, Pt, Au) and CaRhMg₂ – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

Klenner

Reimann

Pöttgen

2021

Zeitschrift Für Kristallographie - Crystalline Materials

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Magnesium and barium in two substructures: BaTMg₂ (T = Pd, Ag, Pt, Au) and the isotypic cadmium compound BaAuCd₂ with MgCuAl₂ type structure

Reimann

Pöttgen

2022

Zeitschrift Für Kristallographie - Crystalline Materials

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The intermetallic barium compounds BaTMg2 (T = Pd, Ag, Pt, Au) and BaAuCd2 were synthesized by reactions of the elements in sealed tantalum ampoules in muffle furnaces. The five compounds crystallize with the orthorhombic MgCuAl2 type structure, space group Cmcm, with small differences in chemical bonding between the magnesium and cadmium series. All samples were characterized through their Guinier powder diffraction patterns. The structures of BaPdMg2 (a = 444.57(4), b = 1174.67(10), c = 827.58(7) pm, wR2 = 0.0460, 475 F 2 values, 16 variables), BaAuMg2 (a = 450.27(6), b = 1183.94(16), c = 838.76(11) pm, wR2 = 0.0355, 473 F 2 values, 16 variables) and BaAuCd2 (a = 463.31(5), b = 1112.79(12), c = 826.63(8) pm, wR2 = 0.0453, 469 F 2 values, 16 variables) were refined from single crystal X-ray diffraction data. The large barium atoms push the [TMg2] respectively [AuCd2] substructures apart. This allows fast moisture attack and leads to fast hydrolyzes of the samples when they get in contact with water. The influence of the difference in electronegativity between magnesium and cadmium is reflected for the pair of compounds BaAuMg2 and BaAuCd2. The magnesium compound shows the higher auridic character, while the cadmium compound shows a tendency towards a three-dimensional cadmium substructure.

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Coloring variants of the Re₃B type

Seidel

Pöttgen

2021

Zeitschrift Für Naturforschung B

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The Re3B type, space group Cmcm, has boron-centered trigonal prisms as central building units and is one of the basic structure types with numerous binary and ternary representatives. The coloring of different atoms on the two crystallographically independent rhenium sites leads to a manifold of compounds with different bonding peculiarities that are rather isopointal than isotypic with the prototype. Typical compounds are the S-phase precipitate MgCuAl2, the silicide ScPt2Si or the iodide Th0.5Pb0.5I3 (PuBr3 type). Differences in size or composition might force symmetry reductions. This is discussed for YZn3 (space group Pnma) and the different coloring variants ScRhSi2 and TaNi2P which show different twists of the trigonal prisms. Striking singular representatives with lower symmetry structures are BaThBr6 (Pmma) and NbCo2B (P21/c) which allow different ordering/distortion patterns for the prisms. All these crystal chemical details are discussed on the basis of group subgroup schemes (Bärnighausen trees).

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Ternary plumbides ATPb₂ (A = Ca, Sr, Ba, Eu; T = Rh, Pd, Pt) with distorted, lonsdaleite-related substructures of tetrahedrally connected lead atoms

Abstract: AbstractThe plumbides CaTPb2 (T = Rh, Pd), EuTPb2 (T = Rh, Pd, Pt), SrTPb2 (T = Rh, Pd, Pt) and BaTPb2 (T = Pd, Pt) were obtained by direct reactions of the elements in sealed tantal… Show more

Cited by 4 publications

References 50 publications

EuTMg₂ (T = Pd, Ag, Ir, Pt, Au), EuTCd₂ (T = Pd, Pt, Au) and CaRhMg₂ – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

EuTMg₂ (T = Pd, Ag, Ir, Pt, Au), EuTCd₂ (T = Pd, Pt, Au) and CaRhMg₂ – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

Magnesium and barium in two substructures: BaTMg₂ (T = Pd, Ag, Pt, Au) and the isotypic cadmium compound BaAuCd₂ with MgCuAl₂ type structure

Coloring variants of the Re₃B type

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Ternary plumbides ATPb2 (A = Ca, Sr, Ba, Eu; T = Rh, Pd, Pt) with distorted, lonsdaleite-related substructures of tetrahedrally connected lead atoms

Abstract: AbstractThe plumbides CaTPb2 (T = Rh, Pd), EuTPb2 (T = Rh, Pd, Pt), SrTPb2 (T = Rh, Pd, Pt) and BaTPb2 (T = Pd, Pt) were obtained by direct reactions of the elements in sealed tantal… Show more

Cited by 4 publications

References 50 publications

EuTMg2 (T = Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

EuTMg2 (T = Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

Magnesium and barium in two substructures: BaTMg2 (T = Pd, Ag, Pt, Au) and the isotypic cadmium compound BaAuCd2 with MgCuAl2 type structure

Coloring variants of the Re3B type

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Ternary plumbides ATPb₂ (A = Ca, Sr, Ba, Eu; T = Rh, Pd, Pt) with distorted, lonsdaleite-related substructures of tetrahedrally connected lead atoms

EuTMg₂ (T = Pd, Ag, Ir, Pt, Au), EuTCd₂ (T = Pd, Pt, Au) and CaRhMg₂ – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

EuTMg₂ (T = Pd, Ag, Ir, Pt, Au), EuTCd₂ (T = Pd, Pt, Au) and CaRhMg₂ – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

Magnesium and barium in two substructures: BaTMg₂ (T = Pd, Ag, Pt, Au) and the isotypic cadmium compound BaAuCd₂ with MgCuAl₂ type structure

Coloring variants of the Re₃B type