Crystal structure of the
ternary compound Sc3Cu7.5Al7.5
Chem.
Met. Alloys 9 (2016)
78-83
https://doi.org/10.30970/cma9.0348
Nastasia KLYMENTIY, Nataliya SEMUSO, Svitlana PUKAS, Yaroslav TOKAYCHUK, Lev AKSELRUD, Roman GLADYSHEVSKII
The crystal structure of a new ternary aluminide, Sc3Cu7.5Al7.5,
was solved by direct methods from X-ray powder diffraction data. It
crystallizes with a partly disordered occupation variant of the structure type Sc3Ni11Ge4
(Pearson symbol hP38, space group P63/mmc, a = 8.4848(1),
c = 8.8593(1) Å). The hexagonal unit cell of Sc3Cu7.5Al7.5
contains 36 atoms, distributed over seven crystallographic sites (Sc atoms: one
site, statistical mixtures of Cu and Al atoms: four sites, Cu atoms alone: two
partly occupied sites). The main feature of the structure is the clustering of
the Sc atoms into triangles with relatively short interatomic
distances (δSc-Sc = 3.446(2) Å). The
coordination polyhedra of the Sc atoms are pentagonal
prisms (with seven capping atoms) and those of the sites occupied by atoms of
the statistical mixtures icosahedra, and those of the remaining Cu atoms trigonal prisms (with three capping atoms) or trigonal antiprisms.
Projection of the unit cell of the
structure of the compound Sc3Cu7.5Al7.5 along
the crystallographic direction [001].
Keywords
Aluminum / Copper / Scandium / X-ray powder
diffraction / Crystal structure / Rare-earth atom triangles