Structural and Electronic Properties of Selected Rutile and Anatase TiO₂Surfaces:  An ab Initio Investigation

Abstract

Five low-index stoichiometric TiO2 rutile and anatase surfaces, i.e., rutile (110), (100), and (001) as well as anatase (101) and (100), have been investigated using different Hamiltonians with all-electron Gaussian basis sets, within a periodic approach. Full-relaxations of the aforementioned surfaces have been essentially carried out at the Hartree-Fock (HF) level, but selected surfaces were treated also using pure and hybrid Density Functional Theory (DFT) models. Mulliken charges, band structures, and total and projected-densities of states have been computed both at the HF and the hybrid DFT (B3LYP and PBE0) levels. As regards DFT, the local density (LDA) and generalized gradient approximations (GGA) have been used. No matter which Hamiltonian is considered, as long as sufficiently thick slabs are taken into account, computed atomic relaxations show an overall excellent agreement with the most recent experimental reports. This is especially true when using hybrid functionals which enable the clarification of some conflicting results. Moreover, both at the LDA and HF levels, we were able to classify the surface relative energies in the following sequence: anatase (101) < rutile (110) < anatase (100) < rutile (100) ≪ rutile (001). Instead, when using PBE, B3LYP, or PBE0, the two most stable surfaces are reversed.

First-principles study of thinTiOxand bulklike rutile nanowires

“…Due to pseudopotentials, exchange-correlation approximation and methods used in calculations, lattice parameters can be slightly different from both experimental [28][29][30] and previous calculated values. [31][32][33][34] The comparison of these results, similar to some recent studies 35,36 comparatively including several different exchange-correlation functionals as well as pseudopotentials suggests that GGA calculations yield slightly better agreement with experimental data. Hence, using GGA approximation, the calculated lattice parameters a and c of rutile are 4.64 ͑4.59͒ and 2.98͑2.96͒ Å, respectively.…”

Universal tight binding model for chemical reactions in solution and at surfaces. III. Stoichiometric and reduced surfaces of titania and the adsorption of water

“…The even-odd oscillations that appear for some surfaces, including rutile (110), 35,36,[38][39][40][41] are well reproduced in our calculations. This is seen in Fig.…”

“…As a matter of fact, the TB results match most closely those obtained with hybrid functionals. 35,40,41 In this respect, the agreement for the anatase surfaces is especially impressive. But even apart from matching particular numbers, the most important result is that the relative ordering of surface energies, namely, E surf (110) < E surf (100) < E surf (001) for rutile, and E surf (101) < E surf (100) < E surf (001) for anatase, is perfectly reproduced.…”

Surface energy and excess charge in (1×2)-reconstructed rutile TiO2(110) from DFT+UÜnal1, Mete2, Ellialtıoğlu3 2011Phys. Rev. B120112View full textAdd to dashboardCite

“…4 we compare relative stabilities of stoichiometric and reconstructed slabs through their surface energies with varying number of Ti-layers. Surface energetics of the stoichiometric slab at the Hartree-Fock and at the standard DFT levels were reported to exhibit odd-even oscillations with the number of layers [34][35][36][37]. Our results show that the oscillation of both the stoichiometric and reduced surface energies with slab thickness settles down by the inclusion of U =5 (Fig.…”