Large, larger, largest – a family of cluster‐based tantalum copper aluminides with giant unit cells. I. Structure solution and refinement

This is the first of two parts, where we report the structure determination of a novel family of cluster‐based intermetallic phases of unprecedented complexity: cF 444‐Al 63.6 Ta 36.4 (AT‐19), a = 19.1663 (1) Å, V = 7040 Å 3 , cF (5928 −  x )‐Al 56.6 Cu 3.9 Ta 39.5 , x = 20 (ACT‐45), a = 45.376 (1) Å, V = 93 428 Å 3 and cF (23 256 −  x )‐Al 55.4 Cu 5.4 Ta 39.1 , x = 122 (ACT‐71), a = 71.490 (4) Å, V = 365 372 Å 3 . The space group is in all three cases. These cluster‐based structures are closely related to the class of Frank–Kasper phases. It is remarkable that all three structures show the same average structure that resembles the cubic Laves phase.