Using Density Functional Theory to Model Realistic TiO2 Nanoparticles, Their Photoactivation and Interaction with Water

TL;DR

This study combines multiscale computational methods to model realistic TiO2 nanoparticles, exploring their structural, electronic, and photoactivation properties, including interactions with water, to bridge simulations with experimental observations.

Contribution

It introduces a multistep approach using SCC-DFTB and DFT to optimize large TiO2 nanoparticles and assess their photoactivation and water interactions, advancing realistic modeling capabilities.

Findings

Optimized structures for TiO2 nanoparticles up to 4.4 nm in size.

Analyzed photoexcitation and electron/hole dynamics in nanoparticles.

Validated SCC-DFTB performance against DFT results for structural and electronic properties.

Abstract

Computational modeling of titanium dioxide nanoparticles of realistic size is extremely relevant for the direct comparison with experiments but it is also a rather demanding task. We have recently worked on a multistep/scale procedure to obtain global optimized minimum structures for chemically stable spherical titania nanoparticles of increasing size, with diameter from 1.5 nm (~300 atoms) to 4.4 nm (~4000 atoms). We use first self-consistent-charge density functional tight-binding (SCC-DFTB) methodology to perform thermal annealing simulations to obtain globally optimized structures and then hybrid density functional theory (DFT) to refine them and to achieve high accuracy in the description of structural and electronic properties. This allows also to assess SCC-DFTB performance in comparison with DFT(B3LYP) results. As a further step, we investigate photoexcitation and photoemission processes involving electron/hole pair formation, separation, trapping and recombination in the nanosphere of medium size by hybrid DFT. Finally, we show how a recently defined new set of parameters for SCC-DFTB allows for a proper description of titania/water multilayers interface, which paves the way for modeling large realistic nanoparticles in aqueous environment.