Geometrical and Fe–Fe interaction effects on the charge distribution of the Fe 3 O 2 BO 3 ludwigite

Matos, Marcílio Castro de; Anda, E. V.; Fernandes, J. C.; Guimarães, R. B.

doi:10.1016/s0166-1280(00)00787-9

Cited by 7 publications

(19 citation statements)

References 10 publications

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“…The Fermi level, defined as the highest occupied band orbital, stays at the top of the t 2g group and does not change from one structure to the other, being, in both cases, E F ϭ -12.04 eV. The first unoccupied narrow band is part of the t 2g group and comes from a strong antibonding Fe-Fe * combination of Fe (2) and Fe(4) [5], the most interacting pair. The Fe(2)-Fe(4) bonding () band spreads in the lower part of the 3d bands, one branch of it clearly shown around -13 eV.…”

Section: Resultsmentioning

confidence: 98%

“…For a general overview of the physical system, the band structure was obtained for the new, distorted phase (below 283 K), and compared with that obtained for the regular structure (above 283 K) [5]. Results are shown in Figure 2 for the 3d Fe bands.…”

Section: Resultsmentioning

confidence: 99%

“…To determine possible stabilizing interactions, different stoichiometries [5] were used in the 2D subunit. The corresponding physical models are represented in Figure 3b,c.…”

Section: Resultsmentioning

confidence: 99%

“…The extended Hü ckel method is very convenient in the study of crystalline and electronic structure relationships and was successfully used in the study of charge distribution of Fe 3 O 2 BO 3 [5].…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…Theoretical studies in Fe 3 O 2 BO 3 have included investigations of charge distribution [5] and a detailed analysis of the magnetic properties of the compound [6]. In another theoretical article [7], the structural transition was analyzed through a comparison between one 1D subunit of Fe 3 O 2 BO 3 with a three-leg-ladder hydrogenic chain.…”

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confidence: 99%

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Electronic structure analysis of two crystalline phases of Fe₃O₂BO₃

Matos

Souza

2005

Int J of Quantum Chemistry

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ABSTRACT:A theoretical electronic structure analysis was performed on two crystalline phases of the homometallic Fe ludwigite, appearing in a structural transition recently found experimentally to occur at 283 K. The extended Hü ckel method was used to study different subunits of the compound, which is known to present low dimensionality in magnetic properties. Total energy calculations show an electronic stability of the low-temperature (distorted) phase, in agreement with experiment. A longitudinal Fe 2ϩ -Fe 2ϩ interaction (perpendicular to the flat planes of the orthorhombic unit cell) appears to be mainly responsible for the stabilization. A contribution of another Fe 2ϩ ion was seen to be related to an enhancement of Fe-O interaction. A remarkable result is the reversal of these results when high spin FeO 6 monomers are considered. In that case, it is the Fe-O interaction in an Fe 3ϩ -Fe 2ϩ -Fe 3ϩ triad which seems to drive the stabilization of the distorted phase. It is suggested that spin effects might be important to the structural transition in Fe 3 O 2 BO 3 .

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

“…To determine possible stabilizing interactions, different stoichiometries [5] were used in the 2D subunit. The corresponding physical models are represented in Figure 3b,c.…”

Section: Resultsmentioning

confidence: 99%

Section: Theoretical Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Electronic structure analysis of two crystalline phases of Fe₃O₂BO₃

Matos

Souza

2005

Int J of Quantum Chemistry

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One‐electron approach to describe charge and orbital order in Mn₂OBO₃

Matos

Oliveira

2006

Int J of Quantum Chemistry

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A detailed study is performed on the band structure of the mixed-valent Mn 2 OBO 3 warwickite, by using the high-spin filling (hsf) scheme in the extended Hückel approach. It is found that charge ordering, found experimentally to be adopted by the compound, is associated with orbital order, represented by the presence of x 2 − y 2 holes in Mn1. The hsf scheme provides considerable improvement in the calculation of charge distribution in the material, as compared with the usual band filling scheme, with both Mn1 and Mn2 cations exhibiting positive charge. In addition, the octahedral distortion around Mn1 is correctly described as a Jahn-Teller (JT) type-distortion. The calculated electronic band structure provides evidence that the Mn warwickite is an insulator, in agreement with experimental data. O1, connected to the JT-like distortion of Mn1, is found to be loosely bound to the structure, as compared with other O-atoms in the lattice, showing a favorable condition in the structural stability of the compound. Comparison is made with the mixed-valent Fe 2 OBO 3 warwickite.

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