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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Electronic correlations and crystal structure distortions in BaBiO3.
Dm Korotin1, V Kukolev, A V Kozhevnikov
1Institute of Metal Physics, Yekaterinburg, Russia. dmitry@korotin.name
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|September 28, 2012
Summary
The GGA + U method accurately models Barium Bismuthate (BaBiO3) by capturing charge ordering and structural distortions. This approach overcomes limitations of standard DFT, providing better agreement with experimental data for this complex insulator.
Area of Science:
- Solid State Physics
- Materials Science
- Computational Chemistry
Background:
- Barium Bismuthate (BaBiO3) exhibits charge ordering of Bi4+ ions into alternating Bi3+ and Bi5+ states, forming an insulator.
- This charge ordering is linked to breathing distortions of BiO6 octahedra, which standard Density Functional Theory (DFT) calculations struggle to reproduce.
- Previous DFT studies combining breathing and tilting distortions qualitatively reproduced the monoclinic structure but underestimated key parameters like the energy gap.
Purpose of the Study:
- To reexamine the BaBiO3 problem using the GGA + U method with a focus on the Bi 6s-band.
- To investigate the suitability of the GGA + U method for materials with high oxidation states and spatially extended Wannier functions.
Main Methods:
- Application of the GGA + U method, incorporating a Hubbard U term, to model BaBiO3.
- Utilized a Wannier function basis set specifically for the Bi 6s-band to account for its extended nature.
- Compared computational results with experimental crystal structure parameters and energy gap values.
Main Results:
- The GGA + U method successfully reproduced the crystal structure instability caused by pure breathing distortions, without requiring octahedra tilting.
- Calculated energy gap values and crystal structure parameters showed good agreement with experimental data.
- Highlighted the difference between spatially extended Bi 6s-symmetry Wannier functions in BaBiO3 and more localized d-band Wannier functions in typical transition metal oxides.
Conclusions:
- The GGA + U method provides a more accurate description of BaBiO3's electronic and structural properties compared to standard DFT.
- This method effectively captures the charge ordering and associated distortions, crucial for understanding BaBiO3 as an insulator.
- The findings emphasize the importance of accounting for the nature of Wannier functions, especially in high oxidation state compounds.
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