Rutile TiO2 Bulk Structural and Vibrational Properties: A DFT Study on the Importance of Pseudopotentials

TL;DR

This study demonstrates how the choice of pseudopotentials and exchange-correlation functionals in DFT calculations significantly affects the accuracy of predicted electronic and vibrational properties of rutile TiO2, emphasizing the importance of appropriate computational methods.

Contribution

It systematically compares different pseudopotentials and functionals in DFT to identify optimal combinations for accurately modeling rutile TiO2 properties.

Findings

Norm-conserving pseudopotentials with GGA match experimental lattice parameters.

LDA with ultrasoft pseudopotentials effectively describes vibrational properties.

Vibrational modes exhibit temperature-dependent asymmetry due to bond length changes.

Abstract

Using first-principal density functional theory (DFT) we explained the importance of pseudopotential for decribing the electronic and vibrational properties of rutile TiO2 (R-TiO2). Calculations were performed using the generalized gradient approximation (GGA), local density approximation (LDA) and hybrid functional (HSE), with normconserving, ultrasoft and projector augmented wave (PAW) pseudopotential. The choice of an appropriate exchange-correlation functionals and the pseudopotential within DFT is critical to explain the different properties of R-TiO2. We found that the lattice parameters predicted by the norm-conserving pseudopotential and GGA are in excellent agreement with experimental data. Our studies reveal that norm-conserving pseudopotentials with GGA exchange-correlations provide much improvement for the prediction of the electronic properties of TiO2. We observed that, using LDA and ultrasoft pseudopotential is an excellent combination to describe the vibrational properties of R-TiO2. Furthermore, we observed the temperature dependent asymmetric nature of vibrational modes due to changes of bond lengths and different lattice vibrations.