Journal
JOURNAL OF CHEMICAL PHYSICS
Volume 135, Issue 5, Pages -Publisher
AIP Publishing
DOI: 10.1063/1.3617244
Keywords
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Funding
- Spanish Ministry of Science [MAT2007-62929, CSD2007-00045, CTQ2009-14596-C02-01]
- Comunidad de Madrid [S2009-PPQ/1551]
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This work investigates crystal lattice, electronic structure, relative stability, and high pressure behavior of TiO2 polymorphs (anatase, rutile, and columbite) using the density functional theory (DFT) improved by an on-site Coulomb self-interaction potential (DFT+U). For the latter the effect of the U parameter value (0 < U < 10 eV) is analyzed within the local density approximation (LDA+U) and the generalized gradient approximation (GGA+U). Results are compared to those of conventional DFT and Heyd-Scuseria-Ernzehorf screened hybrid functional (HSE06). For the investigation of the individual polymorphs (crystal and electronic structures), the GGA+U/LDA+U method and the HSE06 functional are in better agreement with experiments compared to the conventional GGA or LDA. Within the DFT+U the reproduction of the experimental band-gap of rutile/anatase is achieved with a U value of 10/8 eV, whereas a better description of the crystal and electronic structures is obtained for U < 5 eV. Conventional GGA/LDA and HSE06 fail to reproduce phase stability at ambient pressure, rendering the anatase form lower in energy than the rutile phase. The LDA+U excessively stabilizes the columbite form. The GGA+U method corrects these deficiencies; U values between 5 and 8 eV are required to get an energetic sequence consistent with experiments (E-rutile < E-anatase < E-columbite). The computed phase stability under pressure within the GGA+U is also consistent with experimental results. The best agreement between experimental and computed transition pressures is reached for U approximate to 5 eV. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3617244]
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