Molecular dynamics simulation of rutile - anatase heterojunction

Abstract

Density Functional based Tight-Binding (DFTB) method is used to study the structural properties and electronic structure of heterojunction between anatase (100) and rutile (100) surface. The near coincidence site lattice (NCSL) theory is used to construct initial models. The interfaces have been annealed from 0K to 2250K in the linear ramp of 10 ps, followed by equilibration at the constant temperature of 2250 for 5 ps and cooled down 0K with an exponential ramp of 15 ps. Interface structures have been investigated via the partial radial distribution functions (PRDF), coordination number, bond-angle distributions and interatomic distances. We found that both structures have the slightly disorder at the interfaces and the presence of four-coordinate Ti atoms, band offsets are 0.45 eV in the conduction band (CB) and 0.51 eV in the valence band (VB) with rutile is higher than anatase. Electrons migrate from rutile to anatase, while holes migrate in the opposite direction.