First-principles spin-polarized calculations on the reduced and reconstructedTiO2(110) surface

Abstract

We have performed plane-wave pseudopotential density-functional theory calculations on the stoichiometric and reduced TiO 2 ͑110͒ surface, the 2ϫ1 and 1ϫ2 reconstructions of the surface formed by the removal of bridging-oxygen atoms, and on the oxygen vacancy in the bulk. The effect of including spin polarization is investigated, and it is found to give a qualitatively different electronic structure compared with a spin-paired description. In the spin-polarized solutions, the excess electrons generated by oxygen reduction occupy localized band-gap states formed from Ti (3d) orbitals, in agreement with experimental findings. In addition, the inclusion of spin polarization substantially lowers the energy of all the systems studied, when compared with spin-paired solutions. However, spin-polarization does not change the relative stability of the two reconstructions, which remain energetically equivalent. ͓S0163-1829͑97͒02724-0͔

First-principles study of potassium adsorption onTiO2surfaces

“…The location of this state was determined, using band-mapping photoemission experiments, to be about 3 eV above the O 2p band maximum. 15 Theoretical calculations on the reduced ͑110͒ surface have reported similar states at 1-2 eV above the O 2p band 16,17 with the reduced Ti ions inducing local distortions of the lattice at the surface. 16 A more controlled reduction of the surfaces can be achieved by adsorbing species which readily donate electrons to the substrate.…”

“…15 Theoretical calculations on the reduced ͑110͒ surface have reported similar states at 1-2 eV above the O 2p band 16,17 with the reduced Ti ions inducing local distortions of the lattice at the surface. 16 A more controlled reduction of the surfaces can be achieved by adsorbing species which readily donate electrons to the substrate. Control of the exposure of the surface to the adsorbate and measurement of the coverage allows the degree of reduction to be varied and monitored.…”

“…This makes it unnecessary to converge the calculations with respect to the interslab vacuum distance inherent in the supercell approximation used in many plane wave ͑PW͒ studies of TiO 2 surface. 12,16 It has been shown in previous studies that a slab thickness of nine atomic layers ͑three TiO 2 formula units͒ is adequate to model the structure and energetics of this surface accurately. 37 The surface unit cell of the c(2ϫ2) structure is shown in Fig.…”

“…We have used HF theory ͑which has been shown in recent work to provide an accurate description of the ground state energetics and electronic structure of transition metal insulators 17,32 ͒ to examine the K adsorption process in order to better understand the nature of the charge transfer state and its consequences for the geometry and electronic structure. Supplementary calculations were performed using DFT within the local density approximation ͑LDA͒ to facilitate comparisons with previous DFT studies 16,33 of reduced TiO 2 surfaces.…”

Thermodynamics of oxygen defective Magnéli phases in rutile: A first-principles study

“…For example, Lindan et al 53 performed spin polarized calculations in oxygen-defective bulk rutile with a formalism similar to that used in the current study.…”