Molecular dynamics characterization of rutile-anatase interfaces

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 photoactive 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/m(2), and the interfaces appear energetically favorable due to an increase of six-coordinate Ti atoms (Ti-6c). 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.