New Indides EuAuIn₂, EuPdIn₄, GdRhIn₂, YbRhIn₄, and YbPdIn₄

Abstract

New intermetallic indium compounds EuAuIn2, EuPdIn4, GdRhIn2, YbRhln*, and YbPdlru were obtained by reaction of the elements. GdRhIn2 was synthesized in an arc-melting furnace, while EuAuIn2, EuPdln*, YbRhIn4, and YbPdIn4 were prepared in sealed tantalum tubes in a high-frequency furnace. The five compounds were investigated by X-ray diffraction both on powders and single crystals. EuAuIn2 and GdRhIn2 adopt the MgCuA^ type structure with space group Cmcm. Single crystal X-ray data yielded a = 468.1(2), b = 1105.5(4), c = 753.5(4) pm, wR2 = 0.096, 343 F2 values for EuAuIn2 and a = 435.0(1), b = 1013.3(3), c = 783.6(2) pm, wR2 = 0.042, 608 F2 values for GdRhIn2 with 16 variables for each refinement.The two structures may be described as gold or rhodium filled versions of the host lattices Euln2 and Gdlri2 . The three-dimensional indium networks of EuAuIn2 and GdRhIn2 resemble the lonsdaleite structure. Both structures are built up from three-dimensional [Auln2] and [Rhln2] poly anions in which the europium and gadolinium atoms occupy distorted hexagonal tubes. The modulations of the In-In distances within the indium networks are compared with other MgCuAk type indides. EuPdIn4 and YbPdIn4 crystallize with the YNiAU type, space group Cmcm: a = 454.8(2), b = 1703.2(8), c = 738.0(3) pm, wR2 = 0.044, 501 F2 values for EuPdIn4 and a = 445.8(2), b = 1666.0(4), c = 747.3(2) pm, wR2 = 0.050, 711 F2 values for YbPdlru with 24 variables for each refinement. In contrast, YbRhln* adopts the LaCoAU type, space group Pmma: a = 863.7(2), b = 422.5(1), c = 743.1(1) pm, wR2 = 0.051, 467 F2 values and 24 variables. EuPdIn4, YbPdlru, and YbRhlm too consist of three-dimensional [Pdln4] and [Rhln4] polyanions in which the europium and ytterbium atoms are located in distorted hexagonal and pentagonal channels. Common structural motifs of these indides are distorted bcc-like indium cubes which are compared with the structures of Y 2CoIns, YCoIns, EuRh2lns, and elemental indium. Chemical bonding in these indides is briefly discussed.

The Gold-rich Indide Eu5Au17.7In4.3 and its Relation with the Structures of SrAu4.76In1.24 and BaLi4

“…The Au-In distances range from 283 to 309 pm. The shorter ones compare well with the sum of the covalent radii [13] of 284 pm, and they are in a range similar to those of the other europium gold indides [4,6,11,12].…”

“…Since we have not obtained a completely X-ray-pure sample, we could not reliably determine the europium valence via magnetic susceptibility measurements or 151 Eu Mössbauer spectroscopy. However, the comparison of the europium coordinations and the Eu-Au / Eu-In distances with the data of the compounds EuAu 3 In 3 [4], EuAuIn [6], Eu 2 Au 3 -In 4 [11], and EuAuIn 2 [12] with divalent europium, and the structural slabs that occur in these compounds undoubtedly point to divalent europium also in Eu 5 -Au 17.7 In 4.3 .…”

“…The Eu-Au distances range from 310 to 339 pm, close to the sum of the covalent radii [13] of 319 pm. Also in EuAuIn [6] (317 -334 pm), EuAuIn 2 [12] (317 -332 pm), Eu 2 Au 3 In 4 [11] (305 -351 pm), and EuAu 3 In 3 [4] (334 -338 pm) the europium sites have gold atoms as closest neighbors, since the Pauling electronegativity [13] of gold (2.54) is significantly higher than that of indium (1.78). The Eu1 (478 pm Eu1-Eu3) and Eu2 (546 pm Eu2-Eu1) atoms have no close Eu-Eu contacts.…”

“…The structures of equiatomic EuAuIn [6], Eu 2 Au 3 In 4 [11] and EuAuIn 2 [12] are built up from complex threedimensional gold indium polyanionic networks in which the europium atoms fill larger cavities. The polyanionic networks show strong covalent Au-In besides In-In bonding in the indium-richer phases Eu 2 -Au 3 In 4 and EuAuIn 2 .…”

Physical properties of EuPtIn4 intermetallic antiferromagnet

“…Ni, Pd, Au) have been reported to adopt the orthorhombic YNiAl 4 -type structure which contains complex [PtIn 4 ] polyanionic networks with rare-earth atoms filling distorted hexagonal channels (Fig. 1a) [5][6][7][8][9][10][11]. Interestingly, the clear elongation of the b-axis indicates the possibility of a 2D Brillouin zone with cylindrical Fermi surfaces along the b direction.…”