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DFT+U-TiO2_35_preprint.pdf (1.41 MB)
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On the Use of DFT+U to Describe the Electronic Structure of TiO2 Nanoparticles: (TiO2)35 as a Case Study

preprint
submitted on 29.04.2020 and posted on 30.04.2020 by Angel Morales, Stephen Rhatigan, Michael Nolan, Frances Illas
One of the main drawbacks in the density functional theory (DFT) formalism is the underestimation of the energy gaps in semiconducting materials. The combination of DFT with an explicit treatment of electronic correlation with a Hubbard-like model, known as DFT+U method, has been extensively applied to open up the energy gap in materials. Here, we introduce a systematic study where the selection of U parameter is analyzed considering two different basis sets: plane-waves (PWs) and numerical atomic orbitals (NAOs), together with different implementations for including U, to investigate the structural and electronic properties of a well-defined bipyramidal (TiO2)35 nanoparticle (NP). This study reveals, as expected, that a certain U value can reproduce the experimental value for the energy gap. However, there is a high dependence on the choice of basis set and, and on the +U parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in FHI-aims, requires a lower U value than the simplified rotationally invariant approaches as implemented in VASP. Therefore, the transferability of U values between codes is unfeasible and not recommended, demanding initial benchmark studies for the property of interest as a reference to determine the appropriate value of U.

Funding

MICIUN RTI2018-095460-B-I00

María de Maeztu MDM-2017-0767

Generalitat de Catalunya 2017SGR13

MICIUN for a Juan de la Cierva postdoctoral grant (IJCI-2017-31979)

ERA.Net for Materials Research and Innovation (M-ERA.Net 2), Horizon 2020 grant agreement number 685451

Science Foundation Ireland SFI/16/M-ERA/3418 (RATOCAT)

COST Action CA18234

History

Email Address of Submitting Author

michael.nolan@tyndall.ie

Institution

Tyndall National Institute, UCC

Country

Ireland

ORCID For Submitting Author

0000-0002-5224-8580

Declaration of Conflict of Interest

No conflict of Interest

Version Notes

Submitted to JCP

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