  One of the most active research areas in the world is the search for
effective materials for use in the fields of optoelectronics and photovoltaics.
The potential of materials like ATiO3 (A=Ti,Sr) is yet largely untapped. Ab
initio studies based on density functional theory (DFT) have been used to
comprehensively explore the structural, electronic, elastic, and optical
properties of Ti2O3 and SrTiO3. In this study, the ground state properties were
computed with spin-orbit coupling (SOC), without spin-orbit coupling, and with
the inclusion of Hubbard U parameter. The electronic bandgaps of Ti2O3 have
been found to be 0.059 eV without SOC, 0.131 eV with SOC, and 1.665 eV with
Hubbard U. Electronic bandgaps of 1.612 eV, 1.761 eV, and 2.769 eV have been
obtained for SrTiO3, respectively, without SOC, with SOC, and with Hubbard U.
In every single case, it has been found that Ti-4d orbitals predominate close
to the top of the valence band. The bandgap and estimated lattice constants for
ATiO3 (A=Ti,Sr) were not significantly affected by SOC. The mechanical
stability test showed that ATiO3 (A=Ti,Sr) is mechanically stable at zero
pressure. The optical band gap has been seen to increase when Hubbard U is
taken into account. In general, the Hubbard U parameter enhances bandgap and
optical property predictions. Ti2O3 and SrTiO3 are good UV-Vis absorbers and
appropriate for photovoltaic applications owing to the optical absorption
coefficient curves being found to cover the ultraviolet to visible (UV-Vis)
ranges.
