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Intermetallic Gold Compounds RE AuMg ( RE = Y, La–Nd, Sm, Eu, Gd–Yb)
Author(s) -
Pöttgen Rainer,
Hoffmann RolfDieter,
Renger Jan,
Rodewald Ute Ch.,
Möller Manfred H.
Publication year - 2000
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 - 10.1002/1521-3749(200011)626:11<2257::aid-zaac2257>3.0.co;2-#
Subject(s) - intermetallic , materials science , physics , crystallography , metallurgy , chemistry , alloy
New intermetallic rare earth compounds RE AuMg ( RE = Y, La–Nd, Sm, Eu, Gd–Yb) were synthesized by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. Some structures were refined on the basis of single crystal data. The compounds with Y, La–Nd, Sm, and Gd–Tm adopt the ZrNiAl type structure with space group P 62 m : a = 770.8(2), c = 419.5(1) pm, wR 2 = 0.0269, 261 F 2 values for PrAuMg, a = 750.9(2), c = 407.7(1) pm, wR 2 = 0.0561, 649 F 2 values for HoAuMg with 15 variables for each refinement. Geometrical motifs in HoAuMg are two types of gold centered trigonal prisms: [Au1Mg 3 Ho 6 ] and [Au2Mg 6 Ho 3 ]. The gold and magnesium atoms form a three‐dimensional [AuMg] polyanion in which the holmium atoms fill distorted hexagonal channels. The magnesium positions show a small degree of magnesium/gold mixing resulting in the refined compositions PrAu 1.012(2) Mg 0.988(2) and HoAu 1.026(3) Mg 0.974(3) . EuAuMg and YbAuMg contain divalent europium and ytterbium, respectively. Both compounds crystallize with the TiNiSi type structure, space group Pnma : a = 760.6(3), b = 448.8(2), c = 875.8(2) pm, wR 2 = 0.0491, 702 F 2 values, 22 variables for EuAuMg, and a = 738.4(1), b = 436.2(1), c = 864.6(2) pm, wR 2 = 0.0442, 451 F 2 values, and 20 variables for YbAuMg. The europium position shows a small degree of europium/magnesium mixing, and the magnesium site a slight magnesium/gold mixing leading to the refined composition Eu 0.962(3) Au 1.012(3) Mg 1.026(3) . No mixed occupancies were found in YbAuMg where all sites are fully occupied. In these structures the europium(ytterbium) and magnesium atoms form zig‐zag chains of egde‐sharing trigonal prisms which are centered by the gold atoms. As is typical for TiNiSi type compounds, also in EuAuMg and YbAuMg a three‐dimensional [AuMg] polyanion occurs in which the europium(ytterbium) atoms are embedded. The degree of distortion of the two polyanions, however, is different.