First-principles study of strain-induced Jahn–Teller distortions in BaFeO₃

Abstract

The effect of epitaxial strain on structural, magnetic and electronic properties of BaFeO perovskite oxide are investigated from first principles calculations, using the density functional theory (DFT) plus the Hubbard approach (DFT+U) within the generalized gradient approximation. Hybrid functional calculations, based on mixed exact Hartree-Fock and DFT exchange energy functionals, are also performed. For the ground state calculations, the DFT+U is found more suitable to describe the half metallic and ferromagnetic state of cubic BaFeO. Jahn-Teller distortions, oxygen octahedra rotations and charge orderings in BaFeO under biaxial strain are explored. The obtained results reveal that structural changes associated with Jahn-Teller distortions are induced under tensile biaxial strain while the oxygen octahedra rotations and breathing are unusually not observed. Then, the strained BaFeO is considered as a particular Jahn-Teller distorted perovskite with exceptional properties when compared to CaFeO and SrFeO. These findings lead to a strain engineering of the JT distortions in BaFeO, and thus for high fundamental and technological interests.

Structural and Magnetic Properties of BaFeO2.667 Synthesized by Oxidizing BaFeO2.5 Obtained via Nebulized Spray Pyrolysis

“…For comparison, similar calculations were performed on cubic Pm 3̅ m BaFeO 3 . Previous ab initio simulations found that, within the collinear spin polarization, the FM phase is thermodynamically more stable than the AFM phases at 0 K for BaFeO 3 , − and we therefore focus on the FM phase for BaFeO 3 . The reciprocal space of the five-atom cubic primitive unit cell was sampled by a Γ-centered 12 × 12 × 12 mesh; otherwise, the same computational conditions as for Ba 3 Fe 3 O 8 were applied.…”

Interdependence of Oxygenation and Hydration in Mixed-Conducting (Ba,Sr)FeO3−δ Perovskites Studied by Density Functional Theory

“… a The presence or absence of JT distortions is also sensitive with regard to the computational details of the calculations. The balance between the cubic and JT distorted structures was shown to be dependent on the employed exchange–correlation functional …”

Dynamic stabilization of perovskites at elevated temperatures: A comparison between cubic BaFeO$_{\textbf{3}}$ and vacancy-ordered monoclinic BaFeO$_{\textbf{2.67}}$

“…Phase Method U eff (eV) Stability 2017 [14] cub. BaFeO3 DFT+U 5 Stable 2018 [16] cub. BaFeO3 DFT+U 4 Unstable 2018 [15] cub.…”

“…The specific U eff value is not trivial to determine and, as Table I reveals, a small change can lead to qualitatively different results. For example, cubic BaFeO 3 was predicted to be dynamically stable with U eff ≈ 5 eV [14,15], while Jahn-Teller distortions were observed with U eff = 4 eV [16,17]. These differences highlight that the U eff value needs to be chosen with care, ideally by calibration with respect to a higher level method.…”

“…As indicated by the arrows, one imaginary mode e M 1 at the M point [q = (1/2, 1/2, 0)] and two degenerate imaginary modes e R 1 and e R 2 at the R point [q = (1/2, 1/2, 1/2)] are observed, which reveals dynamic instability for the cubic structure at 0 K. The imaginary modes correspond to collective displacements on the O atom sublattice. These displacements are related to the Jahn-Teller effect [16,17] and they deform the octahedra in specific ways as illustrated in Figs. 3(c) and 3(d).…”