Dresden 2011 – scientific programme

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KR: Fachgruppe Kristallographie

KR 5: Poster Multiferroics (Joint Session of MA, DF, DS, KR, TT)

KR 5.70: Poster

Tuesday, March 15, 2011, 10:45–13:00, P2

Role of oxygen holes and charge-dispropotionation in transition-metal compounds,Cs₂Au₂Cl₆ — •Alexey Ushakov¹, Sergey Streltsov^1,2,3, and Daniil Khomskii¹ — ¹II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln Germany — ²Institute of Metal Physics, S. Kovalevskoy Str. 18, 620041 Ekaterinburg GSP-170, Russia — ³Ural Federal University, Mira Str. 19, 620002 Ekaterinburg, Russia

The systems with mixed-valence (MV) state of magnetic ions and/or with spontaneous charge disproportionation attract at the moment big attention. Typical such system is perovskite gold chloride Cs₂Au₂Cl₆. At ambient pressure it is an insulator with tetragonal crystal structure I4/mmm. There appears in this phase a spontaneous charge segregation of Au into Au¹⁺(d¹⁰) and Au³⁺(d⁸), ordered in checkerboard fashion. Under the pressure this valence disproportion vanishes, and at about 11.3 GPa, this systems becomes a metal with equivalent Au (single-valent(SV) state).

In this work we perform the ab-initio band structure calculations of Cs₂Au₂O₆ . The main aim of our research is to determine the factors, which promote the charge disproportionation in this and similar systems, and the possible role of ligand (here Cl) holes in the formation of such state and its change under pressure.