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On the use of DFT+U to describe the electronic structure of TiO2 nanoparticles: (TiO2)35 as a case study
American Institute of Physics
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 the electronic correlation with a Hubbard-like model, known as the 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 the U parameter is analyzed considering two different basis sets: plane-waves 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. 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 on the U parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in Fritz Haber Institute ab initio molecular simulation (FHI-aims), requires, requires a lower U value than the simplified rotationally invariant approach, as implemented in the Vienna ab initio simulation package (VASP). Therefore, the transfer 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.
Density functional theory , DFT , Energy gaps , Semiconducting materials
Morales-García, Á, Rhatigan, S., Nolan, M. and Illas, F. (2020) 'On the use of DFT+U to describe the electronic structure of TiO2 nanoparticles: (TiO2)35 as a case study', Journal of Chemical Physics, 152(24), 244107 (8pp). doi: 10.1063/5.0012271
© 2020, the Authors. Published under license by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author(s) and AIP Publishing. This article appeared as: Morales-García, Á, Rhatigan, S., Nolan, M. and Illas, F. (2020) 'On the use of DFT+U to describe the electronic structure of TiO2 nanoparticles: (TiO2)35 as a case study', Journal of Chemical Physics, 152(24), 244107 (8pp), doi: 10.1063/5.0012271, and may be found at https://doi.org/10.1063/5.0012271