Density functional theory calculations of dense TiO2 polymorphs: implication for visible-light-responsive
Ming-Yu Kuo1, Cheng-Lung Chen, Chih-Yu Hua
1Institute of Materials Science and Engineering and Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan, Republic of China.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
This study calculated electronic band gaps for dense titanium dioxide (TiO2) polymorphs. Fluorite-type TiO2 exhibits the narrowest band gap, suggesting potential for visible-light photocatalysis.
Area of Science:
- Materials Science
- Solid-State Physics
- Computational Chemistry
Background:
- Titanium dioxide (TiO2) is a crucial material with diverse applications.
- Understanding the electronic properties of TiO2 polymorphs is key to optimizing its performance.
- High-pressure or strained conditions can lead to novel TiO2 structures.
Purpose of the Study:
- To investigate the structural parameters and electronic band gaps of dense TiO2 polymorphs.
- To identify TiO2 structures with potential for visible-light photocatalysis.
- To validate computational methods using known TiO2 phases.
Main Methods:
- First-principles density functional theory (DFT) with local-density approximation (LDA).
- Calculation of structural parameters and electronic band gaps for alpha-PbO2, baddeleyite, fluorite, and cotunnite TiO2 structures.
- Validation of calculations against experimental and theoretical data for rutile and anatase TiO2.
Main Results:
- The fluorite-type TiO2 structure was found to possess the narrowest electronic band gap (1.08 or 2.18 eV after correction).
- This narrow band gap is attributed to highly symmetric TiO8 polyhedra with mixed Ti(3d) and O(2p) orbitals.
- Calculations for dense TiO2 polymorphs were validated against known ambient phases.
Conclusions:
- Fluorite-type TiO2, featuring Ti with eight coordinated oxygens, shows promise as a visible-light-responsive photocatalyst.
- The electronic band gap is strongly influenced by the coordination environment of titanium atoms.
- Computational methods provide valuable insights into the properties of high-pressure TiO2 polymorphs.
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