Ab Initio Molecular Dynamics Calculations of the Phase Transformation Mechanism for the Formation of TiO2 Titanate-Type Nanosheets from Anatase

Abstract

This work investigates the transformation mechanism, at atomic level, of anatase to titanate-type structures by carrying out ab initio molecular dynamics (ab-MD) calculations with the Harris functional, including the Γ-point approximation and also several k-points. The transformation mechanism is presented and discussed. Three different size wire models of anatase with periodic conditions along the (0,1,0) direction were used, and several different environment conditions were investigated. It is found that the titanate-type structure is energetically favorable. The transformation was followed by monitoring the formation of four-coordinated oxygen atoms, which constitute the characteristic sequence of edge-sharing TiO6 octahedrons of titanates. Additionally, the titanate-type structure can be transformed to anatase in a reverse mechanism. A very important factor in the transformation of the anatase-type sections to the TiO6 octahedrons is the interaction of the (0,0,±1) surfaces of the anatase with positive charges (Na+), which stress the surface deforming it and promoting the transformation.