Superstructure formation in Sc5Cu2In4

Polycrystalline Sc5Cu2In4 was synthesized by induction melting of the elements and small single crystals were obtained by a slow cooling sequence. Sc5Cu2In4 is the first coinage metal representative in the family of the so-called 5-2-4 intermetallics. The Zr5Ir2In4 type structure of Sc5Cu2In4 was refined from single crystal X-ray diffractometer data: Pnma, a = 1716.75(6), b = 677.94(12), c = 760.69(2) pm, wR2 = 0.0531, 1932 F-2 values and 58 variables. Sc5Cu2In4 adopts a superstructure of the Lu5Ni2In4 type (doubling of the b axis and klassengleiche symmetry reduction from Pbam to Pnma), caused by dislocation of the copper atoms (puckering effect). Geometrically, Sc5Cu2In4 is a 4:1 inter-growth structure of distorted AlB2 and CsCl related slabs.