The Geometry and Electronic Structure of the Cu2+Polyhedra in Trirutile-Type Compounds Zn(Mg)1−xCuxSb2O6and the Dimorphism of CuSb2O6: A Solid State and EPR Study
1997; Elsevier BV; Volume: 131; Issue: 2 Linguagem: Inglês
10.1006/jssc.1997.7374
ISSN1095-726X
AutoresE.-O. Giere, A. Brahimi, H. J. Deiseroth, D. Reinen,
Tópico(s)Advanced Condensed Matter Physics
ResumoResults from crystal structural analyses of CuSb2O6with the trirutile structure, which transforms from theβphase (space groupP21/n) to theα-phase (space groupP42/nmn) at 380 K, are reported. While extensive twinning prevents the single crystal structure determination of theβmodification, theαphase reveals compressed CuO6polyhedra with Cu–O spacings of 202.6 pm (2×) and 206.6 pm (4×). From the spectroscopic investigation (EPR, optical) of mixed crystals Zn(Mg)1−xCuxSb2O6with dependence onxand temperature it is deduced that the CuO6polyhedra are compressed (spacings≅197 pm (2×) and ≅208.5 pm (4×)) forx<0.5 but transform to elongated entities at larger Cu2+concentrations (spacings 200.4 pm (2×), 201.2 pm (2×), and 212.0 pm (2×) from neutron diffraction powder analysis (3)). Evidence for anisotropicπ-contributions to the Cu–O bond is presented. A detailed analysis of the ground state potential surface in terms of a vibronic Jahn–Teller coupling model in the presence of a host site strain is given for the two alternative CuO6geometries. The Cu–O spacings inα-CuSb2O6are explained as resulting from those in theβphase by a dynamic averaging process (201.2 pm (2×), 212.0 pm (2×)→ 206.6 pm (4×) above 380K).
Referência(s)