Computer model of crystallization of binary systems; Kinetic phase transitions

Chernov, A. A.; Lewis, J.

doi:10.1016/0022-3697(67)90243-0

Cited by 57 publications

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“…Metastable phases and assemblages tend to have disordered structures and high entropy configurations of atoms, and they may form more readily in systems initially far from equilibrium (Chernov and Lewis 1967). Irreversible reactions are sensitive to fluid/rock ratio and deformation history, as any parameter that accelerates dissolution will tend to expedite transformation to the more stable assemblage.…”

Section: Variables Affecting Clay Mineral Reactionsmentioning

confidence: 99%

Clay Mineral Thermometry—A Critical Perspective

Essene

Peacor

1995

Clays and clay miner.

229

129

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Abstract--Diagenetic clay minerals usually occur as heterogeneous assemblages of submicroscopic layers consisting of different structure types such as illite, smectite and chlorite, with variable composition within a given structure type, and with highly variable concentrations of imperfections. The dimensions of mixed-layering, the semi-coherent to coherent nature of the structures across the layering, and compositional heterogeneity occur at a scale well below that of an individual thermodynamic phase. These relations imply that most clays are not distinct minerals or phases, and that assemblages of clays in shales and mudstones are incompatible with the phase rule. Such relations are better evaluated in terms of the formation of metastable materials with each small unit having unique chemical properties, rather than as a small number of stable homogeneous phases. Consequently, treatment of most clay minerals in terms of equilibrium stability with either a thermodynamic or experimental approach is subject to error.Chemical reactions involving most clay minerals are best understood with kinetic models. These involve a great variety of parameters such as time, fluid/rock ratio, deformation history, nature of starting materials and transformation mechanisms, as well as the variables, such as temperature, pressure and composition, that are commonly used to define equilibrium. Solubility experiments on the stabilities of clay minerals are unlikely to attain equilibrium at low temperatures. Moreover, the activity of soluble species may be controlled by surface equilibria, or by absorbed or exchangeable cations. Interpretations of available experiments on the solubility of illite vs. other mineral assemblages are in violation of Schreinemakers' rules and indicate lack of equilibrium.Predictable sequences of clay minerals as a function of temperature are best understood through the Ostwald step rule, in which clay mineral assemblages undergo reactions in response to kinetic factors that represent reaction progress rather than an approach to equilibrium. Currently used clay mineral thermometers (illite crystallinity, smectite/illite reaction, chlorite composition) are not based on equilibrium reactions. Such systems are not accurate thermometers and therefore have questionable utility.

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Section: Variables Affecting Clay Mineral Reactionsmentioning

confidence: 99%

Clay Mineral Thermometry—A Critical Perspective

Essene

Peacor

1995

Clays and clay miner.

229

129

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“…5, equal interaction between like particles (i.e., pq.~=fffaa), and various 1-8 interactions, including model ionic interactions and different values of the interaction exponent m. Figure 1 shows results obtained at a fixed undercooling Ap /kT=0. 5 terest, since it contrasts with those of earlier simulations [7] of ionic crystal growth that considered only firstnearest neighbors and neglected bulk diffusion. In Fig. I (e) the interaction energies between neighboring particles are p, ""i/kT=2 3, e. ";", =e""q=0.…”

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confidence: 66%

“…Explicit consideration is given to mutual interactions between like and unlike particles at the solidliquid interface. Previous treatments of the morphologies of binary systems have either been macroscopic continuum theories, which deal with dilute binary alloys [1] or binary eutectics [2], or microscopic theories [3][4][5][6][7]. Apart from the work of Karma [8], microscopic theories have involved statistical models that ignore bulk diffusive transport.…”

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confidence: 99%

Microscopic-growth morphologies in binary systems

1992

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“…The influence of growth kinetics on the crystallization of a disordered phase in the stability field of an ordered phase has been discussed by Chernov and Lewis (1967), for the case of a binary AB alloy. According to their model, a large overstep beyond equilibrium PT conditions is associated with growth of crystals with a large disorder and a high densities of antiphase domain boundaries.…”

Section: Discussionmentioning

confidence: 99%

Growth and ordering processes in synthetic hydrothermal anorthite

1989

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Abstract. Anorthite crystals were synthetized from gel under hydrothermal conditions (P=1000 bar, T=700 ~ C) with run durations from 2 h to l 10 days. The products were observed at room temperature by optical microscopy, X-ray powder diffraction and transmission electron microscopy (TEM). It has been shown that crystallization progresses as a function of time as follows: from t = 2 h to t = 7 days, the proportion of amorphous material decreases from 80 to 0 percent; the average crystal size grows from 1 to 20 ~tm; the number of crystals per unit volume decreases from 2.1011 to 5.108 cm-3, indicating substantial recrystallization. The average A1, Si state of order increases with time and reaches a steady state after seven days. The crystals exhibit a core few micrometers in diameter and a rim whose width increases with time from 1 to l0 gm. The core, highly disordered in A1, Si, displays weak b reflexions and small antiphase domains (APDs), the rim, more ordered in A1, Si, differs from the core by sharp b reflexions and larger APDs extending radially. Both macroscopic results and microscopic observations show that crystals grow by two successive processes: at first, nucleation and growth from gel giving rise to the core, then recrystallization giving rise to the rim.

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Computer model of crystallization of binary systems; Kinetic phase transitions

Cited by 57 publications

References 0 publications

Clay Mineral Thermometry—A Critical Perspective

Clay Mineral Thermometry—A Critical Perspective

Microscopic-growth morphologies in binary systems

Growth and ordering processes in synthetic hydrothermal anorthite

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