Role of Strain Ans Sr-Doping for the Anisotropic Oxygen Diffusion in LaMnO3

A high ionic conductivity is desireable property for cathode materials for
solid oxide fuel cells. LaMnO₃ is a well studied candidate for this applica-
tion. Hence, it is important to understand the oxygen transport mecha-
nism. We find increase in oxygen vacancy formation energy and diffusion
under compressive and tensile strain as well as under Sr-doping using the
density functional theory and nudged-elastic band calculations. The oxy-
gen vacancy sites and diffusion paths are studied. We investigate the effect
of Sr-doping on the anisotropy of the diffusion. Modified strengths of
the Mn and O bonding as well as volume change are identified as fac-
tors that affect the formation/diffusion of vacancies. Furhermore, tensile
strain facilitates enhanced oxygen vacancy diffusion along the [011]/[0 ̄11] direction. The weakening of the Mn- O bonds as well as the distortion of
the MnO6 octahedra hinder diffusion along the [110]/[1 ̄ 10}direction.