Equiatomic AEAuX (AE=Ca−Ba, X=Al−In) Intermetallics: A Systematic Study of their Electronic Structure and Spectroscopic Properties

Abstract

The three intermetallic compounds SrAuGa, BaAuAl and BaAuGa were synthesised from the elements in niobium ampoules. The Sr compound crystallises in the orthorhombic KHg -type structure (Imma, a=465.6(1), b=771.8(2), c=792.6(2) pm, wR =0.0740, 324 F values, 13 variables), whereas the Ba compounds were both found to crystallise in the cubic non-centrosymmetric LaIrSi-type structure (P2 3, BaAuAl: a=696.5(1) pm; wR =0.0427, 446 F values, 12 variables; BaAuGa: a=693.49(4) pm, wR =0.0717, 447 F values, 12 variables). The samples were investigated by powder X-ray diffraction and their structures refined on the basis of single-crystal X-ray diffraction data. The title compounds, along with references from the literature (CaAuAl, CaAuGa, CaAuIn, and SrAuIn), were characterised further by susceptibility measurements and Al and Ga solid-state NMR spectroscopy. Theoretical calculations of the density of states (DOS) and the NMR parameters were used for the interpretation of the spectroscopic data. The electron transfer from the alkaline-earth metals and the group 13 elements onto the gold atoms was investigated through X-ray photoelectron spectroscopy (XPS), classifying these intermetallics as aurides.

Structural Characterization of Intermetallic Compounds by 27Al Solid State NMR Spectroscopy

“…The alkali-metal, alkaline-earth-metal, or rare-earth-metal cations are found in cavities of the polyanions. Depending on the transition metal content, the Al atoms form covalent heteroatomic bonds (e.g., Ba 3 Pt 4 Al 4 , ScPtAl and ScAuAl, or BaAuAl) or are isolated in cases of transition metal or rare-earth rich phases (RET 5 Al 2 , RE 10 TAl 3 , or Na 2 Au 3 Al). The local symmetries surrounding the Al atoms in the respective crystal structures have been depicted along with the NMR data in the following paragraphs.…”

Temperature induced valence phase transition in intermediate-valent YbPd2Al3

“…Na 2 Au 3 Al, 58 AEAuX (AE ¼ Ca-Ba, X ¼ Al-In), 59 AEAu 2 Al 2 (AE ¼ Ca, Sr) 60 2 Since the most electronegative elements acquire additional electron density, a shi towards lower binding energies can be observed in the respective XPS measurements. [58][59][60][61] Fig (green), Yb 0.33 Ca 0.67 Pd 2 Al 3 (blue), and CaPd 2 Al 3 (orange). As can be seen from the plot and the data in Table 2, only minor shi of the 3d 5/2 and 3d 3/2 lines of the Pd reference and the investigated compounds can be observed.…”

Structural, Physical, Theoretical and Spectroscopic Investigations of Mixed‐Valent Eu2Ni8Si3 and Its Structural Anti‐Type Sr2Pt3Al8

“…In the past few years we have started to investigate the ternary EA − T −Al ( EA =Ca, Sr, Ba; T =Pd, Pt, Au) systems ourselves in more detail and extended the knowledge of the few known compounds. Several compounds were synthesized and structurally characterized, e. g. Ca 2 Pt 6 Al 15 [27] (Sc 2 Pt 6 Al 15 type [27] ), CaPtAl 2 [28] (MgCuAl 2 type [29] ), CaAu 2 Al 2 [19b] ( anti ‐ThRu 2 P 2 type [30] ), Sr 2 Pd 2 Al [31] (Ca 2 Pd 2 Ge type [3] ), Sr 2 Pd 4 Al 5 [32] (own type), the incommensurately (3+2)D modulated SrPt 2 Al 2 [33] (CaBe 2 Ge 2 type [20] ), SrPt 3 Al 2 [31] (CeCo 3 B 2 type [34] ), SrPtAl 2 [28] (MgCuAl 2 type [29] ) or BaPtAl 2 [28] (MgCuAl 2 type [29] ), BaAuAl [35] (LaIrSi type [36] ) and Ba 3 Au 5+ x Al 6– x [19b] (own type). All of these compounds exhibit [ T x Al y ] δ− polyanionic networks with the alkaline earth metals occupying voids.…”