DFT-based study of the structural, electronic and hyperfine properties of the semiconducting alloys Sn1-xTixO2: HSE06 and non-regular TB-mBJ approach

We present here a Density Functional Theory-based ab-initio study of the structural and electronic properties of the semiconducting alloys Sn1-xTixO2 for x in the range 0.0 (rutile SnO2) to 1.0 (rutile TiO2). The hyperfine parameters at Sn and Ti sites for each Ti concentration (x) were also determined. The calculations were performed using two complementary methodologies. The pseudopotentials and plane-wave method (PP-PW) was employed for the determination of the equilibrium lattice parameters and the distribution of the Ti impurities in the SnO2 host for each x value. For the study of the electronic properties and hyperfine parameters at the Sn/Ti sites of Sn1-xTixO2 the Full Potential Linearized Augmented Plane-Wave method (FP-LAPW) was applied. In order to obtain a precise description of the band structure and the band gaps of the alloys state-of-the-art exchange and correlation potentials were employed: the Heyd-Scuceria-Ernserhof (HSE06) and the Tran-Blaha modified Becke-Johnson potential (TB-mBJ). HSE06 correctly describe the experimentally reported band gap as a function of x. On the other hand, TB-mBJ fails in the prediction of the band gaps for values of x larger than 0.5. We show here that the TB-mBJ functional can be easily modified to correctly describe the electronic structure of the system under study. This modification is based in a "calibration" of TB-mBJ using the HSE06 results. Finally, our predictions for the hyperfine parameters at the Sn/Ti sites are in excellent agreement with the experimental results, given confidence to our results for the electronic structure of the Sn1-xTixO2 alloys.