Rare Earth-rich Cadmium Compounds RE₂₃T₇Cd₄ (T = Co, Ni, Ru, Rh, Ir, Pt)

Abstract

The rare earth-rich intermetallic compounds RE 23 T 7 Cd 4 (RE = La-Nd, Sm, Gd, Tb; T = Co, Ni, Ru, Rh, Ir, Pt) were synthesized by melting of the elements in sealed tantalum tubes in a highfrequency furnace. They crystallize with the Pr 23 Ir 7 Mg 4 -type structure, space group P6 3 mc, Z = 2. The structures of La 23 Pt 7 Cd 4 (a = 1025.4(2), c = 2319.5(5) pm, wR2 = 0.0425, 2587 F 2 , 74 variables), La 23 Ru 6.87(1) Cd 4 (a = 1015.0(2), c = 2282.8(4) pm, wR2 = 0.0383, 2459 F 2 , 75 variables), and Nd 23 Rh 7 Cd 4 (a = 990.0(2), c = 2239.0(5) pm, wR2 = 0.0507, 2350 F 2 , 74 variables) were refined from single crystal X-ray diffractometer data. Central structural motifs of the RE 23 T 7 Cd 4 compounds are transition metal-centered trigonal prisms of rare earth atoms and Cd 4 tetrahedra. The RE 6 T prisms are condensed via common edges and corners, leading to three-dimensional networks. Typical interatomic distances in the prismatic network and in the Cd 4 tetrahedra are 295 -313 pm La-Pt and 319 -325 pm Cd-Cd, respectively (examplarily for La 23 Pt 7 Cd 4 ).

Ternary Rare-Earth-Metal Nickel Indides RE23Ni7In4 (RE = Gd, Tb, Dy) with Yb23Cu7Mg4-Type Structure

“…According to literature data, all atomic positions are fully occupied in the structure of Yb 23 Cu 7 Mg 4 as well as in most Pr 23 Ir 7 Mg 4 -type compounds. Some deficient occupancies of transition-metal sites were reported for the structure of Pr 23 Ir 7 Mg 4 itself (Pr 23 Ir 6.81 Mg 4 ), Gd 23 Rh 6.86 Mg 4 , and La 23 Ru 6.87 Cd 4 . The largest homogeneity regions were found for Ce 23 Ru 7+ x Al 4– x (0 < x < 2.97) and Ce 23+ y Ru 7+ x Ga 4– x – y (0 < x < 3.00, 0 < y < 0.97) .…”

“…An assignment of the Pr 23 Ir 7 Mg 4 -type structure would seem to be evident given its overwhelming pervasiveness compared to the Yb 23 Cu 7 Mg 4 -type structure (Table ). − Or is it?…”

“…Some deficient occupancies of transition-metal sites were reported for the structure of Pr 23 Ir 7 Mg 4 itself (Pr 23 Ir 6.81 Mg 4 ), 35 Gd 23 Rh 6.86 Mg 4 , 42 and La 23 Ru 6.87 Cd 4 . 38 The largest homogeneity regions were found for Ce 23 Ru 7+x Al 4−x (0 < x < 2.97) 45 and Ce 23+y Ru 7+x Ga 4−x−y (0 < x < 3.00, 0 < y < 0.97). 46 Ru 7 In 4 ) are significantly shorter than in elemental indium (3.25−3.35 Å in the tetragonal body-centered structure of the ambient allotrope).…”

{Ca, Eu, Yb}23Cu7Mg4 as a Step towards the Structural Generalization of Rare Earth-Rich Intermetallics

“…The component interaction in RTX intermetallic systems (R = rare earth metal; T = transition metal; X = other metal) results in many ternary compounds with recurrent stoichiometries in different concentration ranges. These compounds have been widely studied both for their applicative and fundamental properties [1][2][3][4][5][6][7][8][9][10][11][12], and they represent an ever-growing database for studying structural relationships, aiming for simplified descriptions and rational generalizations.…”