Point Defects in Oxide Solid Solutions (IV). Correlated Diffusion of Cations and Vacancies in (Co, Mg)O‐Mixed Crystals

Schnehage, M.; Dieckmann, R.; Schmalzried, H.

doi:10.1002/bbpc.198200020

Cited by 27 publications

(9 citation statements)

References 29 publications

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“…Measurements of the isotope effect for diffusion of both atomic species in -CuZn and equiatomic FeCo confirm that the Manning model is applicable to these disordered metallic alloys (Bakker, 1984, and references therein). The Manning (1971) model was also found to be consistent with tracer diffusion data in (Co,Mg)O (Schnehage et al, 1982) and (Mg,Fe)2SiO4 olivine (Hermeling and Schmalzried, 1984). In each of these solid solutions there is a strong variation in the diffusivities with composition, but -consistent with the Manning (1971) model -the jump frequency ratio of the two cations is essentially independent of composition.…”

Section: Concentrated Systemssupporting

confidence: 71%

“…For cations that diffuse more slowly than Mg and have large correlation coefficients, the isotope effect would be expected to diminish with increasing temperature. The correlation coefficient determined by Schnehage et al (1982) for Co diffusion in MgO, based on measurements of Co and Mg tracer diffusivities in (Co,Mg)O at 1573 K, is in excellent agreement with the correlation coefficients predicted by the DFT calculations at the same temperature, using Eq. 4 (Fig.…”

Section: Periclase (Mgo)supporting

confidence: 66%

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Theoretical constraints on the isotope effect for diffusion in minerals

Orman

Krawczynski

2015

Geochimica et Cosmochimica Acta

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Please cite this article as: Van Orman, J.A., Krawczynski, M.J., Theoretical constraints on the isotope effect for diffusion in minerals, Geochimica et Cosmochimica Acta (2015), doi: http://dx. ABSTRACTIsotopes of the same element generally diffuse at slightly different rates within a mineral, due to the difference in their masses. The magnitude of the mass dependence of the diffusion coefficient depends on the product of the correlation coefficient f (representing the degree to which the diffusion process deviates from a random walk) and the coupling coefficient K (representing the degree to which the motion of an atom during a single jump is coupled to that of other nearby atoms). Whereas K has been found to vary over a relatively narrow range, f can vary over a wide range from ~0 to 1.Diffusive isotope effects are expected to be large for trace and minor cations that diffuse slowly relative to the major cations that occupy the same sites and diffuse by the same mechanism. Diffusive isotope effects are also expected to be large for elements that diffuse rapidly by a simple interstitial mechanism. In both of these cases, the correlation coefficient is similar to or equal to unity. Diffusive isotope effects are reduced when the diffusion process is correlated, as for (1) rapid diffusion of trace and minor cations by a vacancy mechanism, with a low migration barrier for the jump to a vacancy; (2) diffusion by an interstitialcy process, or a process involving interstitial-vacancy pairs; (3) diffusion in grain boundaries and dislocations, where both dimensional restrictions and non-uniformity of the structure enhance correlation. The correlation coefficient can be determined from independent experimental data on the jump frequencies involved in the diffusion process, and/or from theoretical calculations of the jump energies. Quantitative estimates of the isotope effect are made for several cations in periclase, olivine, magnetite and rutile.

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Section: Concentrated Systemssupporting

confidence: 71%

Section: Periclase (Mgo)supporting

confidence: 66%

Theoretical constraints on the isotope effect for diffusion in minerals

Orman

Krawczynski

2015

Geochimica et Cosmochimica Acta

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“…The point defects in (Fe,Mg,Ni)O, responsible for mass transport, are cation vacancies. [6][7][8][9] The point defects in the spinel layer, based on the data available for Fe 3 O 4 [20] and Fe-based spinels, [21] are expected to be cation vacancies at high-oxygen activities and cation interstitials at low-oxygen activities. The boundary reactions can be represented as follows.…”

Section: A Reaction Between Fe and (Ni X Mg 1ϫx )Omentioning

confidence: 99%

“…The point defects responsible for cation diffusion are vacancies, [6][7][8][9] the concentration of which is a function of composition and oxygen partial pressure at a given temperature. Several studies are available for the thermodynamic activities of MgO in (Ni,Mg)O, [10,11] (Fe,Mg)O, [12][13][14][15] and (Co,Mg)O [16][17][18][19] solid solutions.…”

Section: Reaction Couples Fe/(ni X Mg 1ϫx )O Andmentioning

confidence: 99%

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Internal displacement reactions in multicomponent oxides: Part II. Oxide solid solutions of wide composition range

Reddy

Wiggins

Leonard

et al. 2005

Metall Mater Trans A

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Grundlagen der Kinetik mineralbildender Prozesse

Schmalzried

1982

Ber Bunsenges Phys Chem

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The most complex physico‐chemical process “mineral formation in multicomponent system” is discussed in the sense of limiting cases. The following elementary processes are briefly treated: nucleation and formation of new phases, matter transport in one phase multicomponent system, heterogeneous reaction in multicomponent system. In many cases zero, one and two dimensional crystalline defects play an important role for the morphological and kinetical development of minerals. The role of point defect thermodynamics for the transport coefficient and transport theory of crystalline multicomponent systems is pointed out in some detail.

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Point Defects in Oxide Solid Solutions (IV). Correlated Diffusion of Cations and Vacancies in (Co, Mg)O‐Mixed Crystals

Cited by 27 publications

References 29 publications

Theoretical constraints on the isotope effect for diffusion in minerals

Theoretical constraints on the isotope effect for diffusion in minerals

Internal displacement reactions in multicomponent oxides: Part II. Oxide solid solutions of wide composition range

Grundlagen der Kinetik mineralbildender Prozesse

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