Surface and interstitial Ti diffusion at the rutile TiO2(110) surface

Abstract

Diffusion of Ti through the TiO 2 (110) rutile surface plays a key role in the growth and reactivity of TiO 2 . To understand the fundamental aspects of this important process, we present an analysis of the diffusion of Ti ad-species at the stoichiometric TiO 2 (110) surface using complementary computational methodologies of density functional theory corrected for on-site Coulomb interactions (DFT + U) and a charge equilibration (QEq) atomistic potential to identify minimum energy pathways. We find that diffusion of Ti from the surface to subsurface (and vice versa) follows an interstitialcy exchange mechanism, involving exchange of surface Ti with the 6-fold coordinated Ti below the bridging oxygen rows. Diffusion in the subsurface between layers also follows an interstitialcy mechanism. The diffusion of Ti is discussed in light of continued attempts to understand the re-oxidation of non-stoichiometric TiO 2 (110) surfaces.

TiO2 nanocluster modified-rutile TiO2 photocatalyst: a first principles investigation

“…This provides a more responsive description of the short-range bonding terms, and allows the variable-charge advantage of the QEq scheme to be retained 60 . We have found that the behaviour of oxygen within the Hallil model indicates 75 that the energetics of the QEq component underplay the costs of moving the charge both to and from the oxygen and in our calculations we keep the charge on all oxygens fixed to their bulk value of 1.26e -, with only the Ti ions able to transfer charge between themselves using the original charging self-80 energies 56 . This modification better reproduces the very small changes seen in oxygen charge found with DFT+U; further details can be found in refs.…”

“…There is much interest in using the charge equilibration (QEq) scheme of Rappé and Goddard 54,55 for TiO 2 structures, in which the electronegativity of the ions is used to adjust the charge distribution in an adaptive manner. In our recent work, the 45 application of this approach to TiO 2 has been demonstrated via the QEq methodology 56 which allows charge transfer between ions to minimise the electrostatic energy Ees, whilst including contributions from the charging energies for each ion which takes a parabolic form: been achieved, the forces on the ions are used to move them in a standard minimisation or dynamics algorithm. The atomistic model includes short-range potentials to represent the covalent bonding which is significant for TiO 2 .…”

“…This modification better reproduces the very small changes seen in oxygen charge found with DFT+U; further details can be found in refs. 56,59,60 .…”

Composite Coatings Are Formed by Complex Methods

“…Diffusion processes in systems Ti, Cr, Al and other elements involved leading scientists [4], [5], [6], [7] of the world's.…”

Improving the photocatalytic activity of TiO2 through reduction

“…13 Mulheran, et al demonstrated DFT+U and atomistic charge equilibration calculations give accordant results for surface and interstitial Ti diffusion at the rutile TiO2(110) surface. 17 Even though, influence of reductant defects at the TiO2(110)…”