  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.
