Polyhedron Distortions in Tourmaline

Ertl, Andreas; Hughes, John M.; Pertlik, F.; Foit, Franklin F.; Wright, Stephen E.; Brandstätter, F.; Marler, Β.

doi:10.2113/gscanmin.40.1.153

Cited by 119 publications

(62 citation statements)

References 20 publications

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“…The cation influence on the octahedral angular distortion decreases from Li-Al tourmalines with the largest distortion to Mg tourmalines (dravite, uvite) with the smallest distortion. Therefore, the smallest Ti 4+ and Al 3+ cations produce the highest distortion (Ertl et al 2002b).…”

Section: Metrics Of the Yo 6 Octahedronmentioning

confidence: 97%

“…The largest octahedral distortion (Δ oct ) was observed in Al-rich tourmalines elbaite and olenite (Ertl et al 2002b). In the studied set, such tourmalines display a relatively uniform negative correlation of Al to all bond lengths in YO 6 octahedron (Fig.…”

Section: Metrics Of the Yo 6 Octahedronmentioning

confidence: 99%

“…The ZO 6 octahedron is smaller than the YO 6 octahedron and is more distorted. It is connected to the T (3×), Y (2×), and B (2×) sites (Ertl et al 2002b). As mentioned above, ZO 6 octahedra form 3D framework (Bosi 2017).…”

Section: Cationic Sitesmentioning

confidence: 99%

“…The bond-length distortion can be calculated as (Ertl et al 2002b). However, the shape of octahedral and its divergence from the ideal metrics can be also expressed as the ratio of two opposite bond lengths sums, which approximates for the octahedral space diagonals.…”

Section: Octahedral Bond-length Metricsmentioning

confidence: 99%

“…Such distortions are influenced by both the occupying cation size and the neighbouring polyhedra. However, the effects of individual factors are difficult to separate (Ertl et al 2002b). The cation influence on the octahedral angular distortion decreases from Li-Al tourmalines with the largest distortion to Mg tourmalines (dravite, uvite) with the smallest distortion.…”

Section: Metrics Of the Yo 6 Octahedronmentioning

confidence: 99%

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The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

Bačík¹

2018

J. Geosci.

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The structure of tourmaline-supergroup minerals includes two types of octahedral sites: the ZO 6 octahedron is smaller and more distorted than the YO 6 octahedron. The octahedral sites metrics were studied and their dependency on the chemical composition unconstrained by Y,Z-site disorder assignment. Published chemical and structural data were collected from American Mineralogist Crystal Structure Database for tourmaline samples belonging to dravite-schorl, schorl-elbaite (including tsilaisites) and schorl (± dravite)-olenite series. Correlation analysis of this dataset provided the evidence of cation distribution between sites -Al and Mg are disordered between Z and Y sites, while Fe (mostly ferrous), Li and Mn strongly prefer Y site. Irregular cation distribution results in the variable metrics of both octahedra in tourmalines. It is the function of well-balanced relations between cations at octahedral and neighbouring sites based on bond-valence variations due to different ionic charges. Considering Z and Y cations, there is a dependence of the cation charge difference and the octahedral metrics. The most pronounced irregularity of both octahedra was observed in elbaite samples with the largest charge difference between Li and Al. In contrast, "buergerite" samples with trivalent Fe and Al at both octahedral sites have both octahedra almost isometric. Schorl and dravite samples display an increasing metric irregularity related to the Al and Mg content; increase in Mg reduces irregularity because Mg is distributed between both octahedral sites balancing charge difference. In contrast, Fe-rich and Al-rich schorl samples display larger irregularity which may result from selective incorporation of Fe 2+ to the Y site. In olenite samples, the irregularity of both octahedra decreases with an increasing Al content. These variations are related to the shared edge of ZO 6 and YO 6 octahedra including both O3 and O6 site where bonds of both anions are balancing bond-valence requirements of the stable electroneutral structure. In addition to the bond-valence relations, effects of the internal geometry of atomic shells should be also considered, i.e. Jahn-Teller distortion that can be decisive factor in cation occupancy. Especially Fe 2+ can strongly prefer YO 6 octahedron whose prolonged tetragonal dipyramidal geometry is more favourable for Fe 2+ in (t 2g ) 4 (e g ) 2 configuration. Received: 6 October 2017; accepted: 31 May 2018; handling editor: J. Cempírek The online version of this article (doi: 10.3190/jgeosci.260) contains supplementary electronic material. Keywords: tourmaline supergroup, octahedral metrics, bond-valence theory, Jahn-Teller effectvacancies (Henry et al. 2011), although Ti structural position is not clear yet.Although the site occupancy usually follows Goldschmidt rules (ionic radii of cations occupying the Z site are lower and therefore the ZO 6 octahedron is smaller), local structural and bond-valence requirements may result in various cation disorder. Along with the Al-Mg disorder (Hawthorne ...

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Section: Metrics Of the Yo 6 Octahedronmentioning

confidence: 97%

Section: Metrics Of the Yo 6 Octahedronmentioning

confidence: 99%

Section: Cationic Sitesmentioning

confidence: 99%

Section: Octahedral Bond-length Metricsmentioning

confidence: 99%

Section: Metrics Of the Yo 6 Octahedronmentioning

confidence: 99%

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The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

Bačík¹

2018

J. Geosci.

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Onset of Antiferromagnetic Insulator‐to‐Ferromagnetic Half Metal‐to‐Antiferromagnetic Metal Transitions in La_1−xCa_xCrO₃ and their Microscopic Origin

Swami

Dixit

Tiwari

2023

Physica Status Solidi (b)

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The magnetic ground state of LaCrO3 and CaCrO3 solid solution is investigated in the complete miscibility range, that is, La1−xCaxCrO3 with 0 ≤ x ≤ 1 at the interval of x = 0.25 to understand the magnetic phase transitions with Ca substitutional fraction. The density functional theory is used with Hubbard correction to account for Cr exchange interaction. The isostructural La1−xCaxCrO3 system exhibits antiferromagnetic insulator (x = 0, i.e., LaCrO3) to ferromagnetic half metal (x = 0.75, i.e., La0.25Ca0.75CrO3) to antiferromagnetic metal (x = 1, i.e., CaCrO3) phase transitions. Cr changes its oxidation state from 3+ in LaCrO3 to 4+ in CaCrO3, showing both 3+ and 4+ states for intermediate compositions. Interestingly, the introduction of Hubbard energy U and Ca substitution affects Cr–O hybridization, as observed in partial density of states. A compositional phase diagram with magnetic ground state is presented for the La1−xCaxCrO3 (0 ≤ x ≤ 1) system.

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Investigation of structural and electronic properties by pnictogen substitution in the layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb)

Muhammady

Erlyanti

Widita

et al. 2019

Int J of Quantum Chemistry

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We study the structural and electronic properties of p-type layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb), calculated by first principles. Pn substitution from P to Sb increases D 2d-type local symmetry distortions at ZnPn 4 and OLa 4 tetrahedra. (LaO) ZnP and (LaO)ZnAs exhibit direct band gaps (Γ ! Γ) of 0.621 eV and 0.528 eV, respectively, while (LaO)ZnSb exhibits an indirect band gap (Γ ! 0.2Λ) of 0.029 eV. The band gaps come from valence Pn p x /p y and conduction Zn 4s states. Moreover, the substitution increases split-off energy at Z and Γ points. We find localized valence degeneracy-lifted Zn 3d states because of the possible second-order Jahn-Teller effect, which induces the local symmetry distortions. The localized Zn 3d states are followed by minor bonding s-p hybridization of Zn and Pn. Above them, we show major bonding s-p hybridization; O 2p states in electron-blocking [LaO] + layers, which are essential for thermoelectricity; and nonbonding Pn p states near Fermi level. In the conduction band, antibonding s-p hybridization is found. Our result shows new insights and findings of structural and electronic properties, which explain previous experimental results, as the focus of this study is related to inorganic chemistry. This study is important for future functional device applications.

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Polyhedron Distortions in Tourmaline

Cited by 119 publications

References 20 publications

The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

Onset of Antiferromagnetic Insulator‐to‐Ferromagnetic Half Metal‐to‐Antiferromagnetic Metal Transitions in La_1−xCa_xCrO₃ and their Microscopic Origin

Investigation of structural and electronic properties by pnictogen substitution in the layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb)

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Polyhedron Distortions in Tourmaline

Cited by 119 publications

References 20 publications

The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

The crystal-chemical autopsy of octahedral sites in Na-dominant tourmalines: octahedral metrics model unconstrained by the Y,Z-site disorder assignment

Onset of Antiferromagnetic Insulator‐to‐Ferromagnetic Half Metal‐to‐Antiferromagnetic Metal Transitions in La1−xCaxCrO3 and their Microscopic Origin

Investigation of structural and electronic properties by pnictogen substitution in the layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb)

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Onset of Antiferromagnetic Insulator‐to‐Ferromagnetic Half Metal‐to‐Antiferromagnetic Metal Transitions in La_1−xCa_xCrO₃ and their Microscopic Origin