Computer Simulation of Cation Distribution in Dioctahedral 2:1 Layer Silicates Using IR-Data: Application to Mössbauer Spectroscopy of a Glauconite Sample

Dainyak, Lydia G.; Drits, Victor A.; Heifits, L. M.

doi:10.1346/ccmn.1992.0400412

Cited by 34 publications

(21 citation statements)

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“…The cation distribution with the minimum values for N22 and/or NFA corresponding to the number of R2+-R 2+ and Fe3+-A1 pairs, respectively, is accomplished by a penalty function, f(~) = ~/FA + (1-~)N22, where the at parameter is to be pre-set. Dainyak et al (1992) showed that three values of a have a practical meaning: if ~ is zero, pairs RZ+-R2+ should be forbidden in bl or b2 directions, at = 1 implies prohibition of Fe3+-A1 pairs in these directions, and both limitations take place at ~ = 0.5. …”

Section: Ir Spectroscopymentioning

confidence: 99%

“…Dainyak et al (1992) elaborated a computer program in order to distribute four types of cations: Mg, Fe z+, Fe 3+ and A1 within a transvacant octahedral sheet. As basic global parameters of the octahedral cation distribution, the occurrence probabilities Wii (i, j = Mg, Fe z+, Fe 3+, AI) for cations of the i and j types bonded to OH groups were used.…”

mentioning

confidence: 99%

“…The solution to this problem proposed by Dainyak et al (1992) was based on computer simulation of the two-dimensional distribution of octahedral cations in dioctahedral 2:1 layer silicates. Using the experimental data obtained by different methods, this simulation can reconstruct the actual cation distribution in dioctahedral mica structures.…”

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Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mössbauer and EXAFS spectroscopies

et al. 1997

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AB S TRACT: Celadonite, glauconite and Fe-illite samples were studied by XRD, EXAFS, IR and M6ssbauer spectroscopy. The samples were monomineralic and corresponded to IM polytype. In the OH-stretching region of the IR spectra the content of each definite pair of cations bonded to OH groups was determined. The number of heavy (Fe) and light (AI, Mg) octahedral cations nearest to Fe was found by the EXAFS technique. The predicted quadrupole splitting values for each definite arrangement of cations nearest to Fe 3+ were used to interpret the M6ssbauer spectra. After the fitting procedure, the intensity of each doublet corresponded to a definite set of local cation arrangements around Fe 3+ and to a definite occurrence probability of these arrangements. Computer simulation and the experimental data obtained were used to reconstruct the distribution of isomorphous octahedral cations in the 2:1 layers. For all samples, R 2+ cations prefer to occupy one of the two symmetrically independent cis-sites and RZ+-R 2+ and/or AI-Fe 3+ were prohibited in the directions forming _+ 120 ~ with the b axis. Therefore, octahedral sheets of the samples revealed domain structure, in which domains differ in size, in the nature of predominant cation and/or by cation ordering.One of the characteristic features of phyllosilicates and, in particular, dioctahedral micas, is a wide variation of chemical compositions. Different samples of the same mineral may differ not only in octahedral and tetrahedral cation contents of 2:1 layers, but also in their long-and short-range ordering in isomorphous cation distribution. Determination of the actual cation distribution in dioctahedral micas is a complex problem. X-ray diffraction (XRD) yields data only on the averaged composition of cations in the unit-cell sites, ignoring a possible short-range ordering. For finely dispersed minerals containing stacking faults, even this information is often difficult to obtain.Spectroscopic methods are, therefore, especially useful, since they probe local atomic environments and have a potential to determine short-range cation ordering. Utilization of spectroscopic methods, however, often meets certain difficulties. One of the main problems is that most of these methods are indirect, that is, they provide indirect structural information about a sample under study. For this reason, interpretation of spectroscopic data is not always feasible or properly based.One of the effective ways to determine the actual cation distribution consists of the application of complex diffraction and spectroscopic methods to the same sample. Obviously, the greater the number of methods involved, the more comprehensive the structural information obtained. Each method, however, has its own advantages and limitations and therefore provides only a partial solution to a 9 1997 The Mineralogical Society 154 K A. Drits et al.general problem of cation order/disorder in dioctahedral mica structures. Therefore, even if unambiguous interpretation of experimental data is provided, the actual ca...

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Section: Ir Spectroscopymentioning

confidence: 99%

mentioning

confidence: 99%

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Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mössbauer and EXAFS spectroscopies

et al. 1997

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“…Also, they found a tendency of Al and Fe to segregate from each other. Dainyak, Drits, and Heifits (1992) performed Mö ssbauer analysis on a transvacant glauconite and found that it presented celadonite-and illite-like domains in its octahedral sheet and that the crystallographic ''right'' and ''left'' cis-positions in a fixed b direction were not equally occupied by divalent and trivalent cations. Goodman, Nadeau, and Chadwick (1988) studied smectites from bentonites by means of Mö ssbauer and electron paramagnetic resonance spectroscopies and found that Fe was located in two different crystal field environments, which could be interpreted as either two phases, two crystallographic sites, or two different nearest neighbor compositions.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Fe segregation in the octahedral sheet of bentonitic illite-smectite by means of FTIR, 27 Al MAS NMR and reverse Monte Carlo simulations

Cuadros¹

1999

American Journal of Science

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“…There is no problem in considering the presence of those domains in the octahedral sheet in a polar layer. The presence of domains in the octahedral sheet of2:1 phyllosilicates has already been reported (Dainyak et al 1992;Grauby et al 1993Grauby et al , 1994. It is likely that the higher charge in an illitic tetrahedral sheet, or the charge distribution, forces the transformation of the octahedral sheet.…”

Section: Discussionmentioning

confidence: 71%

Some Evidence Supporting the Existence of Polar Layers in Mixed-Layer Illite/Smectite

Cuadros

Linares

1995

Clays and clay miner.

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Abstract--The fraction <20 #m of a bentonitic material was selected to study the transformation of smectite into illite under hydrothermal conditions. Powder XRD showed that the studied material was composed of 97% dio~mhedral smectite and 3% of quartz, cristobalite and plagioclase. The XRD analysis of the oriented, glycolated sample showed that the smectitic phase was actually a randomly interstratified illite/smectite with 11% illite. The chemical analysis of the sample yielded the structural formula: Ko.2sNao.25Cao.12Mgo.~3(A12.7~Feo.33Mgl.o3)(SiT.6~Alo.34)O2o(OH)4. The reaction conditions of the hydrotherreal experiments were: KCI concentrations 0.025, 0.05, 0.1, 0.3, 0.5, 1 M; temperature 60, 120, 175, 20(PC; run time 1, 5, 15, 30, 90, 180 days; solid: solution ratio 1:5. XRD of run products showed an important transformation of smectite into fllite, in contrast with all other techniques (DTA, IR, NMR), which did not detect any transformation of the original material. This suggests that illite quantification in I/S by means of XRD patterns after hydrothermal experiences can be much affected by other variables. The original material and the run products were analysed by means of DTA. The starting material displayed two dehydroxylation peaks, one at 560~ corresponding to illite, and the other at 650"C corresponding to smectite. Quantification of the two dehydroxylation peaks also yielded a content of 11% illite. The run products displayed DTA diagrams in which the smectitic peak remained unaltered, but the illitic one was reduced or eliminated by the presence of exchangeable K in the interlayer. When exchangeable K was removed the illitic dehydroxylation peak appeared again. The coherence of XRD and DTA in quantifying the proportion ofillite layers and the effect of exchangeable K on dehydroxylation of iUite layers in mixedlayer illite/smectite seem to be positive proofs of the existence of polar Myers.

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Computer Simulation of Cation Distribution in Dioctahedral 2:1 Layer Silicates Using IR-Data: Application to Mössbauer Spectroscopy of a Glauconite Sample

Cited by 34 publications

References 16 publications

Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mössbauer and EXAFS spectroscopies

Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mössbauer and EXAFS spectroscopies

Analysis of Fe segregation in the octahedral sheet of bentonitic illite-smectite by means of FTIR, 27 Al MAS NMR and reverse Monte Carlo simulations

Some Evidence Supporting the Existence of Polar Layers in Mixed-Layer Illite/Smectite

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