Structure of a new multicomponent stannide and
comments on the Yarmolyuk-Kripyakevich criterion for Frank-Kasper
phases
Chem.
Met. Alloys 7 (2014) 169-180
https://doi.org/10.30970/cma7.0289
Volodymyr Gvozdetskyi, Roman Gladyshevskii, Viktor Hlukhyy
The structure of a new stannide,
Nb4.4V1.6Ni6Sn0.9, was refined from
X-ray single-crystal diffraction data (P63/mmc, a = 4.9433(5), c = 17.935(3) Å). It appeared to be formed by two substructures: Nb5Ni6.84V0.16Sn0.84 and V12Sn, in the approximate
ratio 9:1. The first substructure, Nb5Ni6(Ni0.84V0.16)Sn0.84, is an ordering variant of the Cs6K7
type and belongs to the family of tetrahedrally
close-packed structures, in which the atoms are surrounded by P- (16 vertices),
Q- (15 vertices), R- (14 vertices), and X- (12 vertices) Frank-Kasper polyhedra. The second substructure, V12Sn, is built from Q-polyhedra
and 20-vertex pseudo-Frank-Kasper polyhedra and
reveals similarities with the Be12Ti type. The list of known
structures with Frank-Kasper polyhedra was updated
and new features governing this family of compounds were discovered. It was
found that, among the number of possible hypothetical structures, only one
combination derived from the Yarmolyuk-Kripyakevich
criterion, is observed for a particular number of icosahedra.
The four Frank-Kasper polyhedra
Keywords
Intermetallics / Tetrahedrally close-packed structure /
Frank-Kasper polyhedra / Yarmolyuk-Kripyakevich
criterion