A computer simulation investigation of brownmillerite-structured Ba2In2O5

Atomistic simulation techniques have been used to investigate the crystal structure and defect energetics of Ba2In2O5. An interatomic potential model was developed that reproduces the orthorhombic brownmillerite structure, with alternating layers of oxygen octahedra and tetrahedra. Defect calculations show that the most energetically favorable intrinsic defects are of the Frenkel type, with an oxygen vacancy on the O(1) site and an oxygen ion in an interstitial position in the tetrahedral layer. Calculated formation energies of electronic defects suggest that Ba2In2O5 will oxidize with the formation of positive holes, contributing the electronic conductivity that is observed experimentally. Finally, consideration of possible oxygen ion migration pathways in the structure found that energy barriers to migration are lowest between equatorial sites of oxygen octahedra in the [001] direction. (C) 1997 Academic Press.