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Ternary Rare Earth Metal Palladium and Platinum Aluminides R 4 Pd 9 Al 24 and R 4 Pt 9 Al 24
Author(s) -
Thiede Verena M. T.,
Fehrmann Birgit,
Jeitschko Wolfgang
Publication year - 1999
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/(sici)1521-3749(199909)625:9<1417::aid-zaac1417>3.0.co;2-s
Subject(s) - crystallography , triclinic crystal system , palladium , monoclinic crystal system , crystal structure , stacking , platinum , materials science , intermetallic , ternary operation , metal , crystal twinning , chemistry , metallurgy , microstructure , catalysis , biochemistry , organic chemistry , alloy , computer science , programming language
The fifteen intermetallic compounds R 4 Pd 9 Al 24 ( R = Gd–Tm) and R 4 Pt 9 Al 24 ( R = Y, Gd–Lu) were prepared by reaction of the elemental components. Their crystal structure was determined from single‐crystal X‐ray data of Er 4 Pt 9 Al 24 . It is pseudo‐trigonal with triclinic symmetry: P 1, a = b = 747.5(2) pm, c = 1306.7(4) pm, α = 100.99(2)°, β = 95.47(2)°, γ = 60.00(3)°, Z = 1, R = 0.052 for 2593 structure factors and 110 variable parameters. The structure is closely related to that of Y 2 Co 3 Ga 9 . Both may be described as stacking variants of each other. They consist of layers of the compositions PtAl 2 (CoGa 2 ), and Er 2 Al 3 (Y 2 Ga 3 ), designated A and B , respectively. These layers are stacked in the five‐ and four‐layer sequences ABAAB (Er 4 Pt 9 Al 24 ) and ABAB (Y 2 Co 3 Ga 9 ). The layers PtAl 2 and CoGa 2 are similar to the hexagonal close packed layers in the TiSi 2 ‐, CrSi 2 ‐, and MoSi 2 ‐type structures. The structure of Er 4 Pt 9 Al 24 contains a monoclinic subcell, where the layers Er 2 Al 3 are disordered. A partial disorder of this kind, which could be ascribed to twinning or to the intergrowth with another stacking variant, was found during the structure refinement of the isotypic compound Y 4 Pt 9 Al 24 : a = b = 749.0(2) pm. c = 1309.3(4) pm, α = 100.99(2)°, β = 95.48(2)°, γ = 60.00(3)°, R = 0.031 for 1435 structure factors and 128 variable parameters.