Regensburg 2013 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 3: Electrical and mechanical properties (DF jointly with KR)
KR 3.1: Vortrag
Montag, 11. März 2013, 15:00–15:20, H11
High-pressure crystal structure of Bi12GeO20 sillenite — •Leonore Wiehl, Alexandra Friedrich, Eiken Haussühl, Wolfgang Morgenroth, and Björn Winkler — Institut für Geowissenschaften, Goethe-Universität, Frankfurt/Main, Germany
Bi12GeO20 crystallizes in the sillenites structure type with the non-centrosymmetric cubic space group I23. Sillenites Bi12MO20 (M = Si, Ge, Ti) are used in technical applications because of their outstanding electrical and nonlinear optical properties, especially the photorefractive effect. These properties are assumed to be correlated with the stereochemical activity of the 6s2 lone electron pair of Bi3+.
The evolution of the Bi12GeO20 crystal structure under high pressure was investigated by experiment and theory using single-crystal X-ray diffraction and density functional theory (DFT) calculations. The crystal structure was determined from X-ray intensity data collected at ambient conditions in house and at high pressure with synchrotron radiation at HASYLAB (D3). Pressures up to 21 GPa were generated in diamond anvil cells. DFT calculations were performed up to 50 GPa. The pressure dependence of interatomic distances indicates a reduced eccentricity of the Bi3+ coordination at high pressure, but not a collapse of the Bi3+ lone electron pair. The results are discussed in comparison with the isotypic Si sillenite [1].
Financial support from the DFG (HA 5137/3-1) and from HASYLAB is gratefully acknowledged. We thank HASYLAB for synchrotron beamtime and Martin Tolkiehn for assistance at D3.
[1] Wiehl L, et al. (2010) J. Phys.: Condens. Matter 22, 505401