Sr substitution effects on atomic and local electronic structure of Ca2AlMnO5+δ

Abstract

We performed the first-principle calculations based on spin-polarized density functional theory to investigate the Sr substitution effects on the atomic and local electronic structure of Ca2AlMnO5+δ. The ionic radius of Sr2+ is larger than that of Ca2+; thus, the lattice expansion occurs with Sr substitution. From the total energy calculations, we found that Sr substitution makes the oxygen-absorbed phase unstable and realizes the lower operation temperature. From the point of atomic structure, Sr substitution lengthens the bond length between Mn and O atoms connecting Mn and Al atoms in Al tetrahedral (OMn-Alt) in oxygen-absorbed phase, because the large Sr2+ prevents the release of the Jahn-Teller distortion. We also found that the covalent bonding between Mn and OMn-Alt atoms weaken with Sr substitution by the local electronic structure analysis, which results in the unstable oxygen-absorbed phase and weak prepeak and main peak intensity near the onset of O-K edge ELNES of OMn-Alt atoms.