Lead-flux Growth of Eu₄Ir₈As₇ Crystals

Abstract

Single crystals of the new arsenide Eu 4 Ir 8 As 7 were grown from a lead flux. The structure was refined on the basis of single-crystal X-ray diffractometer data: Ca 4 Ir 8 P 7 type, P2 1 /m, a = 1311.3(1), b = 408.4(1), c = 1360.3(1) pm, β = 98.45(1) • , wR2 = 0.0640, 1985 F 2 values, 95 variables. The iridium and arsenic atoms in the Eu 4 Ir 8 As 7 structure build up a complex three-dimensional, covalently bonded [Ir 8 As 7 ] network with Ir-As distances ranging from 239 to 260 pm. Each iridium atom has three or four arsenic neighbors in slightly distorted trigonal-planar or tetrahedral coordination. The four crystallographically independent europium atoms fill cavities of coordination numbers 12, 13, and 15 (2 ×) within the [Ir 8 As 7 ] network. Parts of the Eu 4 Ir 8 As 7 structure resemble known simpler structure types, and one can describe the Eu 4 Ir 8 As 7 structure as an intergrowth variant of CaBe 2 Ge 2 -, TiNiSi-and AlB 2 -related slabs.