Tuning the Electronic Structure of Anatase Through Fluorination

Abstract

A highly fluorinated anatase lattice has been recently reported, providing a new class of materials whose general chemical formula is Ti 1 1-x boxx X 4x O 2-4x (X - = F - or OH -). To characterise the complex structural features of the material and the different F environments, we here apply a computational screening procedure. After deriving a polarisable force - field from DFT simulations, we screen in a step-wise fashion a large number of possible configurations differing in the positioning of the titanium vacancies (i) and of the fluorine atoms. At each step only 10% of the configurations are retained. At the end of the screening procedure, a configuration is selected and simulated using DFT-based molecular dynamics. This allows us to analyse the atomic structure of the material, which is strongly disordered, leading to a strong decrease (by 0.8eV) of the band gap compared to conventional anatase.