PNNL

Abstract

We report molecular dynamics (MD) simulations of interfaces between rutile and anatase surfaces of TiO2. These interfaces are important for understanding mixed-phase catalysts, such as the Degussa P25 catalyst, and in particular as a first step toward characterizing electron/hole transport in these photo-active materials. Construction of these interfaces was possible with near-coincidence-site lattice (NCSL) theory. The results suggest adhesion energies for the most stable structures typically near -2 J/m2, and the interfaces appear energetically favorable due to an increase of six-coordinate Ti atoms (Ti6c). Two other notable observations emerge from this work. First, the interfaces are characterized as slightly disordered, with the disorder limited to a narrow region at the interface, in agreement with experiment. Second, formation of rutile octahedral structures was observed at the anatase side of the interface due to surface rearrangement. This appears as the beginning of an anatase-to-rutile phase transition. This work was supported by the Department of Energy, Office of Basic Energy Sciences. Computational resources were provided by the Molecular Science Computing Facility located at the Environmental Molecular Science Laboratory in Richland, WA. All work was performed at Pacific Northwest National Laboratory (PNNL). Battelle operates PNNL for the U.S. Department of Energy. KMR acknowledges the support of the Geosciences program of the DOE Office of Basic Energy Sciences, and the Stanford Environmental Molecular Sciences Institute jointly funded by the National Science Foundation (NSF) and the DOE Office of Biological and Environmental Research.