Abstract
Titanium dioxide (titania, TiO2) is a widely studied material with diverse applications. Here, we explore how pairwise and many-body descriptions of van der Waals dispersion interactions perform in atomistic modeling of the two most important TiO2 polymorphs, rutile and anatase. In particular, we obtain an excellent description of both bulk structures from density-functional theory (DFT) computations with the many-body dispersion (MBD) method of Tkatchenko and co-workers coupled to an iterative Hirshfeld partitioning scheme (“Hirshfeld-I”). Beyond the bulk, we investigate the most important crystal surfaces, namely, rutile (110), (101), and (100) and anatase (101), (100), and (001). Dispersion has a highly anisotropic effect on the different (hkl) surfaces; this directly changes the predicted nanocrystal morphology as determined from Wulff constructions. The periodic DFT+MBD method combined with Hirshfeld-I partitioning appears to be promising for future large-scale atomistic studies of this technological...
Highlights
Titanium dioxide (TiO2) is among the most widely studied metal oxides, owing both to fundamental interest and to diverse applications that range from solar cells and photocatalysis to data-storage devices.[1−4] Atomistic modeling based on densityfunctional theory (DFT) has played a key part in this[5−10] and often with direct links to applications: as but one example, a recent DFT study explored how the material’s rich polymorphism may enable tailored band alignments for optimized photocatalysts.[11]
Labat et al compared the performance of DFT exchange−correlation functionals for the two main TiO2 polymorphs, rutile and anatase,[7] and Arroyo-de Dompablo et al explored the effect of Hubbard-type “+U” corrections.[8]
All the above DFT methods fail to reproduce the experimentally established stability ordering of the main crystalline forms of TiO2: rutile is the stable polymorph at ambient pressure, but DFT predicts anatase to be energetically more favorable.[6]
Summary
Titanium dioxide (TiO2) is among the most widely studied metal oxides, owing both to fundamental interest and to diverse applications that range from solar cells and photocatalysis to data-storage devices.[1−4] Atomistic modeling based on densityfunctional theory (DFT) has played a key part in this[5−10] and often with direct links to applications: as but one example, a recent DFT study explored how the material’s rich polymorphism may enable tailored band alignments for optimized photocatalysts.[11]. Effects of exchange and correlation were modeled in the GGA after Perdew, Burke, and Ernzerhof (PBE),[54] on which the current MBD implementation is based.[29,33] It was previously seen that for ionic solids, higher rung hybrid DFT schemes show good performance when coupled with (pairwise) dispersion corrections; see, for example, studies of NaCl (HSE06+TS)[55] or rutile and anatase TiO2 (PBE0+D2).[23] with future large-scale simulations of surface and nanoparticle models in mind, these hybrid functionals are not computationally feasible at this time, and we focus on their economic GGA counterparts instead. The present, optimized TiO2 surface models at the PBE+MBD level may well provide a starting point for future endeavors of this type
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