Electron Transport via Polaron Hopping in Bulk TiO2: a density functional theory characterization

Journal Article · Tue May 15 04:00:00 EDT 2007 · Physical Review. B, Condensed Matter and Materials Physics, 75(19):Art. No. 195212

DOI:https://doi.org/10.1103/PhysRevB.75.195212· OSTI ID:917932

Deskins, N Aaron; Dupuis, Michel

In this work we describe our use of Marcus theory to model the electron transfer process in TiO2. Electron transport is described by a polaron model, whereby a photo-excited electron is localized at a Ti4+ site and hops to an adjacent Ti4+ site. We obtained the relevant parameters in Marcus theory (namely the activation energy ΔG*, the reorganization energy λ, and the electronic coupling matrix elements Vab) for selected crystallographic directions in rutile and anatase, using periodic DFT+U and Hartree-Fock cluster calculations. The DFT+U method was necessary to correct for the ubiquitous electron self-interaction problem? in DFT. Our results give non-adiabatic activation energies of similar magnitude in rutile and anatase, all near 0.3 eV. The electronic coupling matrix element, Vab, was determined to be largest for electron transfer parallel to the c direction in rutile, with a value of 0.20 eV, while the other directions investigated in both rutile and anatase gave Vab values near 0 eV. The results are indicative of adiabatic transfer (thermal hopping mechanism) in rutile and of diabatic transfer (tunneling mechanism) in anatase. This work was supported by the Office of Basic Energy Sciences of the Department of Energy, in part by the Chemical Sciences program and in part by the Engineering and Geosciences Division. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 917932
• Report Number(s): PNNL-SA-52342; 3564a; KC0302010
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, 75(19):Art. No. 195212, Journal Name: Physical Review. B, Condensed Matter and Materials Physics, 75(19):Art. No. 195212 Journal Issue: 19 Vol. 75; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ACTIVATION ENERGY
ELECTRONS
Environmental Molecular Sciences Laboratory
FUNCTIONALS
MATRIX ELEMENTS
Marcus theory
POLARONS
RUTILE
TITANIUM OXIDES
TRANSPORT
TUNNELING
WAVE FUNCTIONS
adiabatic transfer
diabatic transfer
electron transfer process in TiO2