Tilting structures in spinels

Таланов, В. М.; Широков, В. Б.

doi:10.1107/s0108767312028991

Cited by 21 publications

(26 citation statements)

References 25 publications

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“…The occupancy ratio of Sb and Zn at the octahedral positions is 1:2 [14]. The geometry of the structural tetrahedra and octahedra vary weakly with changes in environmental and crystallization conditions [15]. The β-phase adopts a complex orthorhombic structure [10,16], possibly forming a superstructure [17].…”

Section: Introductionmentioning

confidence: 99%

Structure of a Novel Spinel Li0.5Zn5/3Sb2.5/3O4 by Neutron and Synchrotron Diffraction Analysis

et al. 2017

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Zn 7/3 Sb 2/3 O 4 is a secondary phase in ZnO-based varistors. Acceptor impurities, such as Li + , increase the resistivity. This effect is produced by a modification of the grain boundary barriers. The role of the cationic distribution in the mentioned events is worth clarifying. The Li 0.5 Zn 5/3 Sb 2.5/3 O 4 room-temperature structure was determined by means of a neutron diffraction and synchrotron X-ray diffraction investigation. The title compound was prepared by conventional ceramic process. The elemental composition of the investigated sample was verified by means of electron microscopy-energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The neutron experiment was performed at the high-intensity neutron diffractometer with position-sensitive detector at the D1B beamline of the Laue-Langevin Institute, Grenoble. The high resolution synchrotron measurement was carried out at MCX beamline of Elettra Sincrotrone Trieste. Rietveld analysis was performed with the FullProf program. Li 0.5 Zn 5/3 Sb 2.5/3 O 4 belongs to the spinel family, space group Fd3m (227). The measured lattice parameter is a = 8.5567(1) Å. The Li +1 and Zn +2 ions are randomly distributed among the tetrahedral and octahedral sites as opposed to Sb +5 ions which have preference for octahedral sites. Fractional coordinate of oxygen, u = 0.2596(1), indicates a slight deformation of the tetrahedral and octahedral sites. The data given in this paper provide structural support for further studies on measurements and microscopic explanations of the interesting properties of this family of compounds.

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Section: Introductionmentioning

confidence: 99%

Structure of a Novel Spinel Li0.5Zn5/3Sb2.5/3O4 by Neutron and Synchrotron Diffraction Analysis

et al. 2017

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“…The phases with F43m symmetry can be generated by one-dimensional irrep κ 11 (τ 4 (A 2u )) and can also be generated by two four-dimensional irreps κ 9 (τ 1 ) and κ 9 (τ 4 ) [7][8][9][10]. Below, we will only discuss the phase induced by the irrep κ 11 (τ 4 ) of group Fd3m.…”

Section: Symmetry Of Order Parameter Of Fd3m ↔ F43m Phase Transitionmentioning

confidence: 99%

Universal mechanism of tetrahedral metal cluster formation in structures with breathing pyrochlore sublattices

Таланов¹,

Таланов²

2017

Nanosystems: Phys. Chem. Math.

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A universal mechanism of tetrahedral metal cluster formation in crystal with geometrically frustrated pyrochlore sublattices is proposed. It has been shown that the critical irreducible representation τ , which generated the formation of metal clusters in non-centrosymmetrical F43m-phases from high symmetry phases with Fd3m space group, is a one dimensional irreducible representation κ 11 (τ 4 (A 2u )) (in Kovalev notation). The structural theory of metal cluster formation based on group theoretical calculations was published earlier for the case of A-ordered spinel. In this work, the theory is generalized in the case of any high symmetry Fd3m structures that include pyrochlore sublattices. We presented a brief review of such structures and mechanisms of the tetrahedral metal cluster formation. The existence of so called "breathing" pyrochlore sublattices in ordered phases is predicted theoretically. The groups of atoms, between which bond clusters, are found. These groups of atoms define electron correlation effects. Examples of tetrahedral metal cluster formation in ordered spinels, ordered lacunar spinels, ordered Laves phases (MgCu 4 Sn structural type) and ordered pyrochlore are considered. The theoretical results are confirmed by the known experimental facts.

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“…They are formed as a result of phase transitions from spinel structures. These phases are generated by critical irrep k 10 (τ 1 ) [5,6,14]. Irrep 4(b) are present in regular octahedra (Fig.…”

Section: (D)mentioning

confidence: 99%

“…The analysis of mechanical, permutation and orbital representations of parent structure allowed us to establish that that the structure of Na 4 Ir 3 O 8 is formed as a result of atoms displacements of sodium, iridium and oxygen, and also atoms ordering of sodium, iridium and oxygen [5][6][7][8]. Ordering of all atoms occurs according to the type 1:3.…”

Section: Atomic Hyperkagome Order In Namentioning

confidence: 99%

Atomic order and metallic nanoclusters in Na4Ir3O8

Таланов¹,

Широков²,

Таланов³

2015

Nanosist.: fiz. him. mat.

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A theory for forming Ir-atomic nanoclusters in a dielectric matrix of Na 4 Ir 3 O 8 structure and spinel-like structures is suggested. The atomic order in the Na 4 Ir 3 O 8 structure is investigated by group-theoretical methods of phase transition theory. The critical irreducible representation τ , generating appearance of enantiomorphic P 4 1 32 (P 4 3 32)-phases from high symmetry spinel-like phase with space group Fd3m, is six dimensional irreducible representation k 10 (τ 1 ) (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 Na 4 Ir 3 O 8 are expected. The existence of hyperkagome lattices in six types in ordered spinel structures is theoretically predicted.

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Tilting structures in spinels

Cited by 21 publications

References 25 publications

Structure of a Novel Spinel Li0.5Zn5/3Sb2.5/3O4 by Neutron and Synchrotron Diffraction Analysis

Structure of a Novel Spinel Li0.5Zn5/3Sb2.5/3O4 by Neutron and Synchrotron Diffraction Analysis

Universal mechanism of tetrahedral metal cluster formation in structures with breathing pyrochlore sublattices

Atomic order and metallic nanoclusters in Na4Ir3O8

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