Band gap modulation effect on electronic and optical properties in PbTiO₃under stress: A DFT study

First principles calculation was implemented to explore the effect of band gap modulation under stress in cubic PbTiO3 by using generalized gradient approximation (GGA) and ultrasoft pseudo-potential (USP). The band gaps at different external pressures show indirect band nature with significant reduction in band gapes. The density of states indicated that the upper valence states were influenced by O-2p and in the meantime Ti-d states have main contribution in conduction band. The inclusion of external stress not only changes electronic structure but also significantly changes the optical properties such as complex dielectric function, absorption, energy loss function, refractive index and reflectivity. The shifting of absorption edges toward higher energies confirm the presence of blue shift and make this material an appealing candidate for optoelectronic devices.