Theoretical study of cation substitution in trioctahedral sheet of phyllosilicates. An effect on inner OH group

Scholtzová, Eva; Tunega, Daniel; Nagy, Ladislav Turi

doi:10.1016/s0166-1280(02)00320-2

Cited by 25 publications

(13 citation statements)

References 28 publications

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“…From the experiments on synthetic talcs by Wilkins and Ito (1967) and the rich collection of Farmer (1974), one of the most recent works on analyses of natural talcs having various compositions was published by Petit et al (2004). Their data are in good agreement with the data on these synthetic talcs and with the simulated spectra of 2:1 trioctahedral minerals of the talc type (Scholtzova et al, 2003). The three sets of data are used as standard for absorption band assignments: 3676 cm À1 /mMg 3 OH; 3660 cm À1 /mMg 2 FeOH; 3643 cm À1 /mMgFe 2 OH; and 3621 cm À1 /mFe 3 OH.…”

Section: Ir Spectroscopymentioning

confidence: 55%

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Nkoumbou¹,

Njopwouo²,

Villièras³

et al. 2006

Journal of African Earth Sciences

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Two talc schist occurrences were discovered in the Boumnyebel area, embedded in the Pan-African mica schist, at the junction between Archean, Eburnean and Neoproterozoic formations in Cameroon. They have been analysed by different techniques such as chemical analyses, XRD, DRIFTS, DTA and TG. The talc schist of the northern deposit contains talc (up to 95 wt%) with chlorite, goethite and lepidocrocite as minor minerals. The talc schist of the southern deposit has up to 88% of talc and is speckled with dark green phenoblasts of amphiboles (coexisting prismatic tremolite and magnesio-riebeckite). Due to its high talc content, the amphibole-free talc schist is economically attractive. Chemical analyses show that most of the rocks consist of SiO 2 , MgO and Fe 2 O 3 , except the sample from the southern deposit that displays some amounts of Al 2 O 3 and CaO. Among trace elements, Ni, Co and Cr are as high as in serpentinized peridotites, and suggest a protolith of ultrabasic nature. Chromium concentration in tremolite reaches 6178 ppm; most of the trace elements (Cd, Cr, Dy, Er, Eu, Ga, Gd, Ho, Lu, Nd, Pr, Sm, Sn, Sr, Tb, Tm, Y, Yb, Zr) are compatible with a tremolite lattice. The regional metamorphism yielded garnet micaschist nappes and thus belongs to the upper greenschist facies. Based on the high talc contents of the rocks and occasional coexisting tremolite and magnesio-riebeckite, the origin of the talc deposits is assigned to a hydrothermal alteration of ultramafic rocks. During the hydrothermal event, the fluid composition changed from silica-rich to lime-rich, but very few trace element contents were affected. Thus the low Rb, Sr, Th, Nb, K, Ta, Y, Zr, Hf, MREE and HREE and high Ni, Cr, Co contents of the rocks point to depleted peridotites (harzburgite-lherzolite) and pyroxenite as protoliths. The hydrothermal alteration is expressed in the positive cerium anomaly accompanied by little LREE enrichment of talc-rich rocks and hornblendite. The studied talc schist deposits and the neighbouring gabbroic and ultramafic rocks may belong to a dismembered Pan-African ophiolite set.

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Section: Ir Spectroscopymentioning

confidence: 55%

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Nkoumbou¹,

Njopwouo²,

Villièras³

et al. 2006

Journal of African Earth Sciences

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“…Clusters can be also embedded in the set of point charges in order to mimic the missing part of the 2D solid. Basically, quantum chemistry calculations of kaolinite structure and adsorption effects were investigated using different techniques [2,[13][14][15][16][17][18][19].…”

Section: Models and Methodsmentioning

confidence: 99%

Theoretical Study of Benzene Interaction on Kaolinite

Castro

Martins

2006

J Computer-Aided Mater Des

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Clay minerals represent a growing research area in the development of new materials. Clay and clay-based materials have been widely investigated in efforts to design adsorbents. Furthermore, adsorption has been applied in order to remove organics and as an important strategy to remediate soils and groundwater contaminated with petroleum hydrocarbons. Among clays, kaolinite, Al 2 Si 2 O 5 (OH) 4 , is a layered aluminosilicate of 1:1 clay minerals family. Therefore, we have performed semi-empirical AM1 and ab initio RHF/3-21G* calculations in order to investigate the benzene interaction on kaolinite surface. The cluster model method was employed. Benzene structure was fully optimized. Molecular orbitals and electrostatic potential was also analyzed. The ab initio and semiempirical results shows the benzene molecule largely tilted in relation to the hydroxyl layer. The π orbital of benzene has changed slightly indicating the interaction through the hydroxyl and benzene π orbital.

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“…In previous literature, a number of theoretical studies applying quantum mechanical calculations on uncharged clay minerals can be found for talc, [36][37][38][39] pyrophyllite, 36,[38][39][40][41][42][43][44][45][46] lizardite, 37, 47-50 and kaolinite. [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] However, dispersioncorrected DFT approach was used only in two works: DFT-D2 15 and vdW-TS 22 methods were applied in the calculations of structural parameters of pyrophyllite 46 while the B3LYP-D2 method was used in the study of kaolinite.…”

Section: Introductionmentioning

confidence: 99%

Assessment of ten DFT methods in predicting structures of sheet silicates: Importance of dispersion corrections

Tunega

Bučko

Zaoui

2012

The Journal of Chemical Physics

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124

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The performance of ten density functional theory (DFT) methods in a prediction of the structure of four clay minerals, in which non-bonding interactions dominate in the layer stacking (dispersive forces in talc and pyrophyllite, and hydrogen bonds in lizardite and kaolinite), is reported. In a set of DFT methods following functionals were included: standard local and semi-local (LDA, PW91, PBE, and RPBE), dispersion corrected (PW91-D2, PBE-D2, RPBE-D2, and vdW-TS), and functionals developed specifically for solids and solid surfaces (PBEsol and AM05). We have shown that the standard DFT functionals fail in the correct prediction of the structural parameters, for which non-bonding interactions are important. The remarkable improvement leading to very good agreement with experimental structures is achieved if the dispersion corrections are included in the DFT calculations. In such cases the relative error for the most sensitive lattice vector c dropped below 1%. Very good performance was also observed for both DFT functionals developed for solids. Especially, the results achieved with the PBEsol are qualitatively similar to those with DFT-D2.

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Theoretical study of cation substitution in trioctahedral sheet of phyllosilicates. An effect on inner OH group

Cited by 25 publications

References 28 publications

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Talc indices from Boumnyebel (Central Cameroon), physico-chemical characteristics and geochemistry

Theoretical Study of Benzene Interaction on Kaolinite

Assessment of ten DFT methods in predicting structures of sheet silicates: Importance of dispersion corrections

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