Atomic order and metallic nanoclusters in Na4Ir3O8

M. V. Talanov – Research Institute of Physics, Southern Federal University, Rostov-on-Don, Russia; tmikle-man@mail.ru
V. B. Shirokov – Southern Scientific Center of Russian Academy of Sciences, Rostov-on-Don, Russia; shirokov-vb@rambler.ru
V. M. Talanov – South-Russian State Polytechnical University, Novocherkassk, Russia; valtalanov@mail.ru

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 k101) (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

DOI 10.17586/2220-8054-2015-6-3-442-450


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