  Mn is used as a dopant to improve the electromechanical properties of
perovskite oxides. We elucidate the role of Mn defects and associated vacancies
on the electronic, atomic and ferroelectric properties of BaTiO$_3$. Using
density functional theory (DFT) and DFT+U we investigate the equilibrium
geometry and electronic properties of Mn ion on A or B sites and with
compensating oxygen vacancies. We study the change in the oxidation state of Mn
in response to local environment changes, such as the presence of oxygen
vacancies.

Materials Science