Zirconium and Hafnium

Bradley, D. C.; Thornton, Peter

doi:10.1016/b978-0-08-018864-5.50006-0

Cited by 9 publications

(2 citation statements)

References 197 publications

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“…DFT modeling and UV-Vis spectra simulations [RI-ADC (2)] of dimeric monooxo-bridged and double oxo-bridged Zr(IV)-AcAc units in solid gels The sol-gel process involves condensation reactions and dehydroxylation (the formation of oxo bridges -O-), and thus the formation of polymeric species with mono-(or double) hydroxo (−OH-) or oxo (−O-) bridges is expected [40][41][42][43]. These oligomers consist of repeat units that determine the main photophysical and vibrational properties of the zirconia gel material.…”

Section: Dft Modeling and Uv-vis Spectra Simulations [Tddft And Adc(2mentioning

confidence: 99%

DFT modeling, UV-Vis and IR spectroscopic study of acetylacetone-modified zirconia sol-gel materials

et al. 2011

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Theoretical and spectroscopic studies of a series of monomeric and dimeric complexes formed through the modification of a zirconium butoxide precursor with acetylacetone and subsequent hydrolysis and/or condensation have been performed by applying DFT/B3LYP/6-31++G(d) and highly accurate RI-ADC(2) methods as well as IR and UV-Vis transmittance and diffuse reflectance spectroscopies. Based on DFT model calculations and simulated and experimental UV-Vis and IR spectra of all the studied structures, the most probable building units of the Zr(IV)-AcAc gel were predicted: the dimeric double hydroxo-bridged complex Zr(2)(AcAc)(2)(OH)(4)(OH)(2br) 9 and the monooxo-bridged complex Zr(2)(AcAc)(2)(OH)(4)O(br)·2H(2)O 12. In both structures, the two AcAc ligands are coordinated to one Zr atom. It was shown that building units 9 and 12 determine the photophysical and vibrational properties of the gel material. The observed UV-Vis and IR spectra of Zr(IV)-AcAc gel were interpreted and a relation between the spectroscopic and structural data was derived. The observed UV-Vis bands at 315 nm and 298/288 nm were assigned to partial ligand-metal transitions and to intra-/inter-AcAc ligand transitions, respectively.

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Section: Dft Modeling and Uv-vis Spectra Simulations [Tddft And Adc(2mentioning

confidence: 99%

DFT modeling, UV-Vis and IR spectroscopic study of acetylacetone-modified zirconia sol-gel materials

et al. 2011

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“…Hafnium fluorohydrates are dissimilar to their Z r equivalents, and lose water more readily, implying that the Hf-F bond is stronger (Hf-F 2.10 A in 8 coordination F-OH complexes, Rickards and Waters 1964). Hexachlorohafnates are more soluble in aqueous phases and more resistant to hydrolysis than the Z r equivalents (Bradley and Thornton 1973) and hence implies that Hf will be more stable in a fluid phase, and therefore more mobile than Zr.…”

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confidence: 99%

Geochemical Characteristics of the Nigerian anorogenic province

Batchelor

1987

Geol. J.

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The anorogenic granitoids of Nigeria are classic exampl& of ring complexes associated with migrating mid-plate magmatisin. Most complexes represent eroded calderas of once active volcanoes, and range from 1 to 30 km in diameter. Petrology varies from peraluminous biotite granite, through hypersthene and fayalite granites to peralkaline aegirine. riebeckite-arfvedsonite granites rich in perthitic alkali feldspar. The complexes have intruded crystalline bascmcnt of Pan-African age. and dating indicates a progressive younging to the south.The majority of the Nigerian anorogenic ring-complexes represent the roots of volcanoes with dominantly syenitic to granitic compositions. They are A-type granites of long-time duration. petrologically similar to. hut chronologically older than. their counterparts to thc north in Niger. In a fcw northern centres the volcanic rocks are preserved indicating an alkaline trend through hawaiite. mugearite, trachyte to rhyolite. Some mixing of contrasting magma compositions has occurred to produce trachyandesitic suites with deisequilibrium mineral reactions. Mixing can be identified from the major and trace chemical variations and petrological instability reactions.Extensive mineralization by columbite. cassiterite, sphalerite and wolframitc suggest fluid interaction on a major scale which has affected much of the original mineral asscmhlages. In cases of extreme fluid activity, granites habe bccn converted into microclinites, albitites and greisens. Chemical data for major and trace elements have heen obtained for a comprehensive suitc of Mesozoic volcanic and plutonic rocks from Nigeria. Analyses of the crystalline basement rocks arc presented for comparative purposes. Pctrogenetic trends have been highlighted using selected hivariate diagrams in an attempt to reach a consensus view of the chemical evolution of the province, with due rcgard given to the effects of post-intrusion subsolidus Huid interactions. The series Rb. Th. Nb. La. Cc, Zr, Hf. and Y have been selected to monitor crystal-fluid partitioning. with the more compatible elcments showing greater partitioning to the fluid phase.

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Theoretical predictions of properties and volatility of chlorides and oxychlorides of group-4 elements. I. Electronic structures and properties of MCl4 and MOCl2 (M = Ti, Zr, Hf, and Rf)

Pershina

Borschevsky

Iliaš

2014

The Journal of Chemical Physics

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Relativistic, infinite order exact two-component, density functional theory electronic structure calculations were performed for MCl4 and MOCl2 of group-4 elements Ti, Zr, Hf, and element 104, Rf, with the aim to predict their behaviour in gas-phase chromatography experiments. RfCl4 and RfOCl2 were shown to be less stable than their lighter homologs in the group, tetrachlorides and oxychlorides of Zr and Hf, respectively. The oxychlorides turned out to be stable as a bent structure, though the stabilization energy with respect to the flat one (C(2v)) is very small. The trend in the formation of the tetrachlorides from the oxychlorides in group 4 is shown to be Zr < Hf < Rf, while the one in the formation of the oxychlorides from the chlorides is opposite. All the calculated properties are used to estimate adsorption energy of these species on various surfaces in order to interpret results of gas-phase chromatography experiments, as is shown in Paper II.

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Zirconium and Hafnium

Cited by 9 publications

References 197 publications

DFT modeling, UV-Vis and IR spectroscopic study of acetylacetone-modified zirconia sol-gel materials

DFT modeling, UV-Vis and IR spectroscopic study of acetylacetone-modified zirconia sol-gel materials

Geochemical Characteristics of the Nigerian anorogenic province

Theoretical predictions of properties and volatility of chlorides and oxychlorides of group-4 elements. I. Electronic structures and properties of MCl4 and MOCl2 (M = Ti, Zr, Hf, and Rf)

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