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Berardo E, Hu HS, van Dam HJJ, Shevlin SA, Woodley SM, Kowalski K, Zwijnenburg MA. Describing Excited State Relaxation and Localization in TiO2 Nanoparticles Using TD-DFT. J Chem Theory Comput 2014; 10:5538-48. [PMID: 26583237 DOI: 10.1021/ct500787x] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We have investigated the description of excited state relaxation in naked and hydrated TiO2 nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials: B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled-cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be the inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock like exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT problems during excited state relaxation for certain particles. We hypothesize that the spurious stabilization of CT states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries from those obtained using TD-CAM-B3LYP or TD-BHLYP. Finally, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in small naked and hydrated TiO2 nanoparticles is predicted to be associated with a large Stokes' shift.
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Affiliation(s)
- Enrico Berardo
- Department of Chemistry, University College London , 20 Gordon Street, WC1H 0AJ London, U.K
| | - Han-Shi Hu
- William R. Wiley Environmental Molecular Science Laboratory, Battelle, Pacific Northwest National Laboratory , K8-91, P.O. Box 999, Richland, Washington 99352, United States
| | - Hubertus J J van Dam
- William R. Wiley Environmental Molecular Science Laboratory, Battelle, Pacific Northwest National Laboratory , K8-91, P.O. Box 999, Richland, Washington 99352, United States
| | - Stephen A Shevlin
- Department of Chemistry, University College London , 20 Gordon Street, WC1H 0AJ London, U.K
| | - Scott M Woodley
- Department of Chemistry, University College London , 20 Gordon Street, WC1H 0AJ London, U.K
| | - Karol Kowalski
- William R. Wiley Environmental Molecular Science Laboratory, Battelle, Pacific Northwest National Laboratory , K8-91, P.O. Box 999, Richland, Washington 99352, United States
| | - Martijn A Zwijnenburg
- Department of Chemistry, University College London , 20 Gordon Street, WC1H 0AJ London, U.K
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