  Semiconducting oxides possess a variety of intriguing electronic, optical,
and magnetic properties, and native defects play a crucial role in these
systems. In this study, we study the influence of native defects on these
properties of $\alpha$-MoO$_{3}$ using the first-principles density functional
theory (DFT) calculations. From the formation energy calculations, it is
concluded that Mo vacancies are difficult to form in the system, while O and
Mo-O co-vacancies are energetically quite favorable. We further find that
vacancies give rise to mid-gap states (trap states) that remarkably affect the
magneto-optoelectronic properties of the material. Our calculations indicate
that a single Mo vacancy leads to half-metallic behavior, and also induces a
large magnetic moment of 5.98 $\mu_{B}$. On the other hand, for the single O
vacancy case, the band gap disappears completely, but the system remains in a
non-magnetic state. For Mo-O co-vacancies of two types considered in this work,
a reduced band gap is found, along with an induced magnetic moment of 2.0
$\mu_{B}$. Furthermore, a few finite peaks below the main band edge are
observed in the absorption spectra of configurations with Mo and O vacancies,
while they are absent in the Mo-O co-vacancies of both types, just like in the
pristine state. From the ab-initio molecular dynamics simulations, stability
and sustainability of induced magnetic moment at room temperate is verified.
Our findings will enable the development of defect strategies that maximize the
functionality of the system, and further help in designing highly efficient
magneto-optoelectronic and spintronic devices.
