Octahedral distortions in the homometallic Fe ludwigite

Matos, Marcílio Castro de

doi:10.1016/j.jssc.2004.10.018

Cited by 9 publications

(20 citation statements)

References 15 publications

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“…Realistic geometry-dependent electron-lattice interactions were studied by using the extended Hückel methodology with high spin band electronic configuration; local geometrical distortions of the oxygen octahedra were found to be related to the opening of a gap at the Fermi level of the minority spin band of the 424 triad [21]. The same methodology was used in an extensive study of spin exchange in both crystalline structures of Fe 3 O 2 BO 3 [22].…”

Section: Introductionmentioning

confidence: 99%

First principles calculation of magnetic order in a low-temperature phase of the iron ludwigite

Matos

Terra

Ellis

et al. 2015

Journal of Magnetism and Magnetic Materials

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a b s t r a c tThe magnetic order of a low-temperature dimerized phase of Fe 3 O 2 BO 3 is investigated through a density functional approach which considers full non-collinear spin-spin interactions, focusing on the 15 K crystalline structure. It is found that Fe spins in the (Fe-Fe) 5 þ dimer, formed during the room temperature structural change of Fe 3 O 2 BO 3 , are parallel and have little freedom to rotate under interaction with neighbor Fe atoms. While the Fe dimer behaves as a heavy single magnetic unit the spin magnetic moment of the third Fe 3 þ atom of the Fe triad has, on the contrary, much more freedom to rotate. This is responsible for a canted spin ordering, revealed by a rotation of $ 801 of the trivalent Fe spin relative to the spin orientation of the dimer, due to spin-spin interaction with divalent Fe atoms outside the triad. Canting is thus seen to be responsible for the very low net magnetization, experimentally observed in this compound (T o 40 K).

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Section: Introductionmentioning

confidence: 99%

First principles calculation of magnetic order in a low-temperature phase of the iron ludwigite

Matos

Terra

Ellis

et al. 2015

Journal of Magnetism and Magnetic Materials

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“…Ashared and distorted octahedra, where the oxygen groups are shared by Co (mono‐μ‐oxo bridges) with trigonal BO 3 moiety has been drawn in order to visualize the crystal structure as shown in Figure b. The mixed valent Co 3 BO 5 has been formulated as Co 2 Co′BO 5 , where Co is divalent and Co′ is trivalent ,. The position of both Co 3+ (M2, M3) and Co 2+ (M1, M4) have been indicated by numbering the metal ions as 1,2,3and 4.…”

Section: Resultsmentioning

confidence: 99%

“…The mixed valent Co 3 BO 5 has been formulated as Co 2 Co'BO 5 , where Co is divalent and Co' is trivalent. [34,35] The position of both Co 3 + (M2, M3) and Co 2 + (M1, M4) have been indicated by numbering the metal ions as 1,2,3and 4. The sites of Co 3 + is less compared to Co 2 + .…”

Section: Preparation Of Working Electrode and Electrochemical Charactmentioning

confidence: 99%

Mixed Valent, Distorted Cobalt Ludwigite (Co₃BO₅/Co₃O₂BO₃) and Its Composite with Reduced Multiwalled Carbon Nanotubes (R‐MWCNT) in Enhancing the Domain Edge‐Sharing Oxygen as Superior Water Oxidation Electrocatalysts

et al. 2018

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Herein, we report, a hybrid of mixed valent cobalt ludwigite (Co3BO5) and reduced‐multiwalled carbon nanotubes (R‐MWCNTs) as an outstanding oxygen evolution reaction (OER) electrocatalyst. Interestingly, the composite acts as a potential OER electrocatalyst, displaying a low overpotential of 270 mV @10 mA cm−2, which is lower than that for the state‐of‐the‐art RuO2 catalyst. The remarkable OER performance of the cobalt‐ludwigite is attributed to its basic distorted open crystal structure, which has a relatively high crystal volume, owing to a domain network consisting of edge‐sharing octahedra. Moreover, X‐ray photoelectron spectroscopy clarifies the hybrid of cobalt‐ludwigite and R‐MWCNTs, exhibiting a stable π‐cation‐like interaction between the Co3+ of Co3BO5 rather than Co2+ and neutral π‐ cloud of R‐MWCNTs, which helps in enhancing the conductivity of the system. Thus, the overall performance of the composite stems from the basic crystal structure of the Co3BO5 and the existence of synergistic effects between the R‐MWCNTs on Co3BO5 through π‐cation‐like interaction. Hence, the results of this study might be useful in developing more efficient other ludwigite–carbon OER electrocatalysts as affordable alternatives.

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“…There are ways, however, in which semiquantitative analysis of spin interactions can be done that provide reliable qualitative estimates or overviews based, for instance, on property trends in a series of similar complexes 4, 5. An approach that is somewhat related to the semi‐empirical treatment of spin interactions is the use of a high‐spin band‐filling (hsf) scheme, in which crystalline orbitals are filled according to the high‐spin configuration of the metal 6. Within this approach, a successful analysis of the effects of local distortions on the band structure of a mixed‐valent Fe oxyborate, the ludwigite Fe 3 O 2 BO 3 , was carried out based on the extended Hückel theory 7.…”

Section: Introductionmentioning

confidence: 99%

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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Octahedral distortions in the homometallic Fe ludwigite

Cited by 9 publications

References 15 publications

First principles calculation of magnetic order in a low-temperature phase of the iron ludwigite

First principles calculation of magnetic order in a low-temperature phase of the iron ludwigite

Mixed Valent, Distorted Cobalt Ludwigite (Co₃BO₅/Co₃O₂BO₃) and Its Composite with Reduced Multiwalled Carbon Nanotubes (R‐MWCNT) in Enhancing the Domain Edge‐Sharing Oxygen as Superior Water Oxidation Electrocatalysts

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

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Octahedral distortions in the homometallic Fe ludwigite

Cited by 9 publications

References 15 publications

First principles calculation of magnetic order in a low-temperature phase of the iron ludwigite

First principles calculation of magnetic order in a low-temperature phase of the iron ludwigite

Mixed Valent, Distorted Cobalt Ludwigite (Co3BO5/Co3O2BO3) and Its Composite with Reduced Multiwalled Carbon Nanotubes (R‐MWCNT) in Enhancing the Domain Edge‐Sharing Oxygen as Superior Water Oxidation Electrocatalysts

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

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Mixed Valent, Distorted Cobalt Ludwigite (Co₃BO₅/Co₃O₂BO₃) and Its Composite with Reduced Multiwalled Carbon Nanotubes (R‐MWCNT) in Enhancing the Domain Edge‐Sharing Oxygen as Superior Water Oxidation Electrocatalysts

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