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

摘要

This is the first of two parts, where we report the structuredetermination of a novel family of cluster-based intermetallicphases of unprecedented complexity: cF444-A163.6Ta36.4 (AT-19), a = 19.1663 (1) A, V = 7040 A3, cF(5928 — x)-A156.6013.9M39.5, x = 20 (ACT-45), a = 45.376 (1) V =93 428 A3 and cF(23 256 — X)-A155.4CU5.4Ta39A, x = 122 (ACT-71), a= 71.490 (4) A, V= 365 372 A3. The space group is F43min all three cases. These cluster-based structures are closelyrelated to the class of Frank—Kasper phases. It is remarkablethat all three structures show the same average structure thatresembles the cubic Laves phase.