NANOSYSTEMS: PHYSICS, CHEMISTRY, MATHEMATICS, 2015, 6(3), P. 442-450
Atomic order and metallic nanoclusters in Na4Ir3O8
M. V. Talanov – Research Institute of Physics, Southern Federal University, Rostov-on-Don, Russia; email@example.com
V. B. Shirokov – Southern Scientific Center of Russian Academy of Sciences, Rostov-on-Don, Russia; firstname.lastname@example.org
V. M. Talanov – South-Russian State Polytechnical University, Novocherkassk, Russia; email@example.com
A theory for forming Ir-atomic nanoclusters in a dielectric matrix of Na4Ir3O8 structure and spinel-like structures is suggested. The atomic order in the Na4Ir3O8 structure is investigated by group-theoretical methods of phase transition theory. The critical irreducible representation τ, generating appearance of enantiomorphic P 4132 (P 4332)-phases from high symmetry spinel-like phase with space group Fd3m, is six dimensional irreducible representation k10(τ1) (in Kovalev designation). Ir and Na atoms form an intriguing atom ordering, giving rise to a network of corner shared Ir triangles, called a hyperkagome lattice. It is shown that inside the hyperkagome lattice, there are closed metal contours of chemical bonds formed by Ir-clusters – decagons. Unusual physical properties of solid solutions on the basis of Na4Ir3O8 are expected. The existence of hyperkagome lattices in six types in ordered spinel structures is theoretically predicted.
Keywords: hyper-kagome order, ordered spinels, decagons, nanoclusters.
PACS 61.50.Ks; 36.40.-c