Modelling Surface Atomic Structure of Perovskite Oxide La0.6Sr0.4FeO3 Under Realistic Thermodynamic Conditions

La_0.6Sr_0.4FeO₃ (LSF) is recognized as a leading perovskite oxygen electrode, widely used in various energy applications, such as solid oxide fuel cells and electrolysis cells. Although catalytic reactions primarily occur on the surface, the specific atomic structures and formation of interfaces at the surface remain unclear. This talk will offer a thorough analysis of the bulk and surface thermodynamics of LSF perovskite oxides through a combination of quantum chemistry calculations and Grand Canonical Monte Carlo (GCMC) simulations. The chemical potentials (<i>µ</i>), essential for surface energy calculations, are determined by selecting a physically meaningful and practical approach within the multi-component chemical potential space. The chemical potentials of the cations, influenced by oxygen partial pressure (<i>P</i>_O2), bulk oxygen vacancy concentration (<i>V</i>_O<i>%</i>), bulk cation vacancy concentration (<i>V</i>_M<i>%</i>), and bulk composition (<i>x</i>_La/<i>x</i>_Sr ), are calculated by considering equilibria with relevant reference states. Bulk thermodynamic calculations show the LSF phase diagram regarding decomposition reactions. Within LSF's stable regime, the stable phases under varying oxygen chemical potentials serve as reasonable initial structure guesses for GCMC simulations. These simulations provide insights into the realistic surface and interface structures of LSF under different environmental conditions. Surface segregation of SrO₂, SrO, La₂O₃, and exsolution of Fe is observed at different oxygen chemical potentials. The resulting surface phase diagram highlights the predominance of SrO segregation under ambient conditions. This methodology offers valuable insights into the surface thermodynamics of LSF perovskite oxides, laying the foundation for future research and experimental validation.