WHANGBO, Myung-Hwan; KOO, H.-J.; VILLESUZANNE, Antoine; POUCHARD, Michel

doi:10.1021/ic0110427

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WHANGBO, Myung-Hwan
Department of Chemistry

KOO, H.-J.
Department of Chemistry

VILLESUZANNE, Antoine
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

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Inorganic Chemistry. 2002-04-08, vol. 41, n° 7, p. 1920-1929

American Chemical Society

Résumé en anglais

The perovskites LaMnO(3) and CaFeO(3) consisting of high-spin d(4) transition metal ions undergo different types of distortions, i.e., a Jahn-Teller distortion in LaMnO(3) and a charge disproportionation in CaFeO(3). We investigated the electronic factor causing this difference on the basis of first principles spin-polarized electronic band structure calculations for their ideal cubic structures and also tight-binding electronic band structure calculations for their ideal cubic and distorted structures. Our study shows that a charge disproportionation is favored over a Jahn-Teller distortion in CaFeO(3) because the covalent character is strong in the Fe-O bond, while the opposite is true for LaMnO(3) because the covalent character is weak in the Mn-O bond. In spin-polarized electronic band structure calculations, the covalency of the M-O (M = Fe, Mn) bond is enhanced in the up-spin bands but is reduced in the down-spin bands. Our analysis shows that electron-electron repulsion causes the energy gap between the metal 3d and the oxygen 2p orbitals to become larger for the down-spin than for the up-spin-orbital interactions. Thus in the d-block e(g) bands of both LaMnO(3) and CaFeO(3) the metal 3d orbital contribution is larger in the down-spin than in the up-spin bands.< Réduire

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Perovskites

Metal

Oxygen

Chemical bonding

Inorganic compounds

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Effect of metal-oxygen covalent bonding on the competition between Jahn-Teller distortion and charge disproportionation in the perovskites of high-spin d(4) metal ions LaMnO(3) and CaFeO(3).

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