Ab-initio Electronic and Structural Properties of Rutile Titanium Dioxide

Abstract

Ab-initio, self-consistent electronic energy bands of rutile TiO2 are reported within the local density functional approximation (LDA). Our first principle, non-relativistic and ground state calculations employed a local density functional approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). Within the framework of the Bagayoko–Zhao–Williams (BZW) method, we solved self-consistently both the Kohn–Sham equation and the equation giving the ground state charge density in terms of the wave functions of the occupied states. Our calculated band structure shows that there is significant O 2p–Ti 3d hybridization in the valence bands. These bands are well separated from the conduction bands by an indirect band gap of 2.95 eV, from Γ to R. Consequently, this work predicts that rutile TiO2 is an indirect band gap material, as all other gaps from our calculations are larger than 2.95 eV. We found a slightly larger, direct band gap of 3.05 eV, at the Γ point, in excellent agreement with experiment. Our calculations reproduced the peaks in the measured conduction and valence bands densities of states, within experimental uncertainties. We also calculated electron effective mass. Our structural optimization led to lattice parameters of 4.65 and 2.97 Å for a0 and c0, respectively with a u parameter of 0.3051 and a bulk modulus of 215 GPa.