Ab-initio Electronic and Structural Properties of Rutile Titanium Dioxide

TL;DR

This study uses ab-initio methods to analyze the electronic structure and properties of rutile TiO2, revealing its indirect and direct band gaps, hybridization effects, and structural parameters with high accuracy.

Contribution

First-principles calculations of rutile TiO2's electronic structure and structural properties using the BZW method within LDA, providing detailed band gaps and density of states consistent with experiments.

Findings

Rutile TiO2 has an indirect band gap of 2.95 eV and a direct gap of 3.05 eV.

Calculated lattice parameters and bulk modulus match experimental data.

Reproduced experimental density of states and effective mass values.

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, and 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 O2p-Ti3d hybridization in the valence bands. These bands are well separated from the conduction bands by an indirect band gap of 2.95 eV, from {\Gamma} 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 {\Gamma} 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 {\AA} and 2.97 {\AA} for a_{0} and c_{0}, respectively with a u parameter of 0.3051 and a bulk modulus of 215 GPa.