Structural, electronic and optical properties of LiNbO3 using GGA-PBE and TB-mBJ functionals: A DFT study

In the present work, first-principles calculations were performed to obtain the structural, electronic and optical properties of lithium niobate crystal using two exchange-correlation functionals (GGA-PBE and TB-mBJ). The calculated structural parameters were very close to the experimental values. TB-mBJ functional was found to be good when compared to LDA and GGA functionals in case of bandgap energy of 3.715 eV of lithium niobate. It was observed that the upper valence and lower conduction bands consist mainly the O-2p and Nb-4d states, respectively. Furthermore, calculations for real and imaginary parts of frequency-dependent dielectric function epsilon(omega) of lithium niobate crystal were performed using TD-DFT method. The ordinary refractive index n(omicron)(omega), extraordinary refractive index n(e)(epsilon), its birefringence and absorption peaks in imaginary dielectric function epsilon(2)(omega) were also calculated.