Quantum-chemical modeling of smectite clays

Aronowitz, S.; Coyne, Lelia M.; Lawless, James G.; Rishpon, Judith

doi:10.1021/ic00140a003

Cited by 47 publications

(28 citation statements)

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“…to determine differences between cation substitution into tetrahedral or octahedral sites, due to a lack of sufficiently accurate AG~ values. The quantum-chemical model of smectites of Aronowitz et al (1982) did not consider tetrahedral layer substitution for Si, but did calculate that the favored cations for the octahedral sites were A13+ > Fe 3+ > Mg 2+ > Fe 2+ > Na § > K +.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Tetrahedral Iron in Smectite: A Critical Comment

Cardile¹

1989

Clays and clay miner.

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Section: Theoretical Considerationsmentioning

confidence: 99%

Tetrahedral Iron in Smectite: A Critical Comment

Cardile¹

1989

Clays and clay miner.

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“…To circumvent this lack of experimental information (Aronowitz et al, 1982) undertook quantum-chemical calculations which revealed that, indeed, electron delocalization in the excited state could be anticipated for smectite clays. Interspersed states in the band gap associated with isomorphically substituted AI in the tetrahedral layer and Mg in the octahedral layer are also anticipated.…”

Section: Electronic Absorptionmentioning

confidence: 99%

A possible energetic role of mineral surfaces in chemical evolution

Coyne

1985

Origins Life Evol Biosphere

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The postulated roles of clays and other minerals in chemical evolution and the origin of life are reconsidered in terms of the interaction of these minerals with penetrating sources of energy such as ionizing radiation and mechanical stress. This interaction, including such facets as excitation, degradation, storage, and transfer, is considered here with regard to its profound potential for altering the capabilities of minerals to serve both as substrates for prebiological chemistry and as inorganic prototypic life forms. The interaction of minerals and energy in relationship to surface chemistry is discussed in terms of the spectroscopic properties of minerals, the interaction of energy with condensed phases, some commonly accepted concepts of heterogeneous catalysis in the absence of electronic energy inputs, and some commonly accepted and novel means by which surface activity might be enhanced in the presence of energy inputs. An estimation is made of the potential contribution of two poorly characterized prebiotic energy sources, natural radioactive decay and triboelectric energy. These estimates place a conservative lower limit on their prebiotic abundance. Also some special properties of these energy sources, relative to solar energy, are pointed out which might give them particular suitability for driving reactions occurring under geological conditions. Skeletal support for this broadly defined framework of demonstrated and potential relationships between minerals, electronic excitation, and surface reactivity, as applied to chemical evolution, is provided from the results of our studies on 1/1 clays. We have discovered and partially characterized a number of novel luminescent properties of these clays, that indicate energy storage and transfer processes in clays. These luminescent properties are interpreted in relationship to the electron spin resonance phenomena, to provide a basis for estimating the potential significance of energy storage and transduction in monitoring or driving clay surface chemistry. Consideration of the electronic structure of abundant minerals in terms of band theory and localized defect centers provides a predictive theoretical framework from which to rationalize the capacity of these materials to store and transduce energy. The bulk crystal is seen as a collecting antenna for electronic energy, with the defect centers serving as storage sites. The clay properties produced by isomorphic substitution appear to be intimately associated with all of the life-mimetic chemical processes that have been attributed to clays.(ABSTRACT TRUNCATED AT 400 WORDS)

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“…The increase in the M6ss-bauer VaFe2+ resonance intensity of Li+.-montmorillonite relative to that for Na +-montmorillonite observed here (Table 1) suggests that the phonon energy of WFe2+ may be reduced more by the presence of high-field Li + than by Na + cations. Aronowitz et al (1982) and Leonard and Weed (1970) have suggested that the presence of exchange ions has a significant role in determining electron density patterns in silicate layers. More specifically, Callaway and McAtee (1985) proposed that the influence of exchange cations near basal surface oxygens should alter the electronegativity of the cations to which these oxygens are coordinated, namely WA13 + and WFe 3 +.…”

Section: Unheated Montmorilionitesmentioning

confidence: 99%

Thermally induced cation migration in Na and Li montmorillonite

Luca

Cardile²

1988

Phys Chem Minerals

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Abstract. In order to determine whether Li + cations penetrate into the octahedral layers of montmorillonites upon mild heating (Hofmann-Klemen effect) 57Fe M6ssbauer spectra of Na § and Li § exchanged montmorillonite were obtained before and after treatment at 220 ~ C. The 57Fe nucleus was used as a remote probe to detect electronic perturbations which would occur if a Li cation was to move into the octahedral layer from the interlayer after heating.The ambient M6ssbauer spectra showed that a high charge density interlayer cation such as Li § is effective in reducing the phonon energy of WFe2 +. In addition the EFG at octahedral sites can be significantly modified by interlayer cations as evidenced by the larger quadrupole splitting value measured for the Li § sample with respect to the Na § Interlayer collapse and migration of exchange cations into the montmorillonite lattice after heating to 220 ~ C resulted in the oxidation of the riFe2+ and a decrease in site distortion for WFe3+. Similar spectral parameters for the Fe 3 § resonances of both Na +-and Li+-heated samples suggested the interlayer cations do not penetrate as far as the octahedral layers. In order to utilize the enhanced sensitivity of VIFe2+ A values to changes in EFG the Fe 3 § in the heated montmorillonites was reduced to Fe 2 § with hydrazine. Similar spectral parameters for both the Na +-and Li+-exchanged montmorillonite were observed giving further evidence that Li cations do not migrate into vacant octahedral sites.

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Quantum-chemical modeling of smectite clays

Cited by 47 publications

References 0 publications

Tetrahedral Iron in Smectite: A Critical Comment

Tetrahedral Iron in Smectite: A Critical Comment

A possible energetic role of mineral surfaces in chemical evolution

Thermally induced cation migration in Na and Li montmorillonite

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