Describing Excited State Relaxation and Localization in TiO2 Nanoparticles Using TD-DFT

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• 作者：Enrico Berardo ; Han-Shi Hu ; Hubertus J. J. van Dam ; Stephen A. Shevlin ; Scott M. Woodley ; Karol Kowalski ; Martijn A. Zwijnenburg
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2014
• 出版时间：December 9, 2014
• 年：2014
• 卷：10
• 期：12
• 页码：5538-5548
• 全文大小：520K
• ISSN：1549-9626

文摘

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鈥揊ock 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鈥?shift.