Molecular-scale mechanisms of crystal growth in barite

Pina, Carlos M.; Becker, Udo; Risthaus, Peter; Bosbach, Dirk; Putnis, Andrew

doi:10.1038/26718

Cited by 218 publications

(230 citation statements)

References 11 publications

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“…Because barite scale formation can be impeded by the addition of growth inhibitors, most relevant studies to date have concentrated on understanding the mechanisms of barite crystal growth in the presence and absence of growth inhibitors. [2][3][4][5] Other studies have explored the possibility of enhancing the barite dissolution rate with chelating agents. 6,7 The (001) and (210) surfaces are the dominant barite surfaces expressed under most experimental conditions, both for natural and synthetic crystals.…”

Section: Introductionmentioning

confidence: 99%

Structure of Barite (001)− and (210)−Water Interfaces

et al. 2001

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The structures of the barite (001) and (210) cleavage surfaces were measured in contact with deionized water at 25°C. High resolution (∼1 Å) specular X-ray reflectivity and atomic force microscopy were used to probe the step structures of the cleaved surfaces and the atomic structures of the barite-water interfaces including the structures of water near the barite-water interfaces. The barite (001) and (210) cleavage surfaces are characterized by large (>2500 Å) domains separated by unit-cell steps (7.15 and 3.44 Å steps for the (001) and (210) surfaces, respectively). This observation was unanticipated for the (001) surface in which adjacent BaSO 4 layers are displaced vertically by c/2 and symmetry related through a 2 1 screw axis along (001). The atomic structures of the two cleavage surfaces derived by X-ray reflectivity reveal that near-surface sulfate groups exhibit significant (∼0.4 Å) structural displacements, while Ba surface ion displacements are significantly smaller (∼0.07 Å). Water adsorbs to the barite surfaces in a manner consistent, in both number and height, with the saturation of broken Ba-O bonds; no evidence was found for additional structuring of the fluid water near the surface.

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Section: Introductionmentioning

confidence: 99%

Structure of Barite (001)− and (210)−Water Interfaces

et al. 2001

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“…Soon thereafter, both mechanisms were demonstrated (6, 7), forever sensitizing investigators of crystal growth to the coexistence and dichotomy of spirals and loops. Later it was discovered that crystals containing screw axes normal to the growth face could exhibit interlacing step patterns that, despite having morphologies that were more complex than crystals with proper symmetry axes, were easily understood (8)(9)(10). Hexagonal L-cystine crystals studied here by real-time in situ atomic force microscopy (AFM) exhibit extremely puzzling patterns: Single dislocations apparently form closed loops whereas pairs of dislocations generate spirals.…”

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confidence: 99%

“…Such features can appear to violate a classic theory of crystal growth enshrined more than 60 y ago and could lead to incorrect conclusions about growth mechanisms. sharing a screw axis (8), including 6 1 , and observed for lower-order screw axes (9,10,16,17). The L-cystine spirals are distinguished by well-defined steps corresponding to each elementary layer as well as the six steps belonging to a single elementary layer, permitting direct measurement of the step velocity anisotropy that is responsible for the deceptive microscopic morphologies.…”

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confidence: 99%

Illusory spirals and loops in crystal growth

Shtukenberg

Zhu

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The theory of dislocation-controlled crystal growth identifies a continuous spiral step with an emergent lattice displacement on a crystal surface; a mechanistic corollary is that closely spaced, oppositely winding spirals merge to form concentric loops. In situ atomic force microscopy of step propagation on pathological L-cystine crystals did indeed show spirals and islands with step heights of one lattice displacement. We show by analysis of the rates of growth of smaller steps only one molecule high that the major morphological spirals and loops are actually consequences of the bunching of the smaller steps. The morphology of the bunched steps actually inverts the predictions of the theory: Spirals arise from pairs of dislocations, loops from single dislocations. Only through numerical simulation of the growth is it revealed how normal growth of anisotropic layers of molecules within the highly symmetrical crystals can conspire to create features in apparent violation of the classic theory.B urton, Cabrera, and Frank (BCF) (1-3) launched the modern era of crystal growth (4) with the idea that screw dislocations on a crystal surface continually extrude steps to which molecules can attach. The "living ends" of these emanating spirals resolved the paradox of fast growth from solutions at low supersaturation. BCF theory, conceived originally for simple centrosymmetric cubic lattices, anticipated that one screw dislocation would generate a spiral whereas a closely spaced pair of dislocations spiraling in opposite directions would annihilate one another to form closed loops (the so-called Frank-Read source mechanism) (5). Soon thereafter, both mechanisms were demonstrated (6, 7), forever sensitizing investigators of crystal growth to the coexistence and dichotomy of spirals and loops. Later it was discovered that crystals containing screw axes normal to the growth face could exhibit interlacing step patterns that, despite having morphologies that were more complex than crystals with proper symmetry axes, were easily understood (8-10). Hexagonal L-cystine crystals studied here by real-time in situ atomic force microscopy (AFM) exhibit extremely puzzling patterns: Single dislocations apparently form closed loops whereas pairs of dislocations generate spirals. Although careful analysis has resolved this apparent contradiction and confirmed the correctness of BCF theory, these observations vividly illustrate how crystals lacking proper rotation axes and containing several translationally nonequivalent growth units can produce unusual and deceptive morphological features that can lead to incorrect conclusions about growth mechanisms.L-cystine crystals can form in the kidneys, leading to cystinuria, a painful and chronic condition. Our laboratory has used in situ AFM measurements of step growth rates on well-developed (0001) faces of hexagonal L-cystine (noncentrosymmetric space group P6 1 22, ref. 11) in the presence of additives to identify potent growth inhibitors (12). Remedies of this sort, however, must build on a ...

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“…A related model discussed by Pina et al (1998) for the aqueous growth of barite considers the underlying atomic structure of the growth surface also with reference to PCBs, and the specific energetics of atomic attachment. AFM observations show that at high supersaturations nucleation on the barite (100) surface is initiated at a screw dislocation, but does not proceed classically.…”

Section: Molecular Modelsmentioning

confidence: 99%

Nucleation, Growth, and Aggregation of Mineral Phases: Mechanisms and Kinetic Controls

Benning

Waychunas

2008

Kinetics of Water-Rock Interaction

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The formation of any phase, whether natural or synthetic (Fig. 7.1), is usually a disequilibrium process that follows a series of steps until a thermodynamically stable state (equilibrium) is achieved. The first step in the process of creating a new solid phase from a supersaturated solution (either aqueous or solid) is called nucleation. A particle formed by the event of nucleation usually has a poorly ordered and often highly hydrated structure. This particle is metastable with respect to ordering into a well-defined phase, which can accompany growth of the particle. This process of initiation of a new phase is defined as a first order transition and can follow various pathways involving a host of mechanisms. One of these pathways occurs when individual nuclei coalesce into larger clusters, a process defined as aggregation, which itself can follow a series of different pathways. The new phase is thermodynamically defined when the growing nucleus or aggregate has distinct properties relative to its host matrix; for example, a well-defined crystal structure, composition and/or density. These processes depend on a plethora of chemical and physical parameters that control and strongly affect the formation of new nuclei, the growth of a new crystal, or the aggregation behavior of clusters, and it is these issues that will be the focus of this chapter. We will discuss the mechanisms and rates of each process as well as the methods of quantification or modeling from the point of view of existing theoretical understanding. Each step will be illustrated with natural examples or laboratory experimental quantifications. Complementary to the information in this chapter, a detailed analysis of the mechanisms and processes that govern dissolution of a phase are discussed in detail in Chap. 5 and more detailed information about molecular modeling approaches are outlined in Chap. 2.

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Molecular-scale mechanisms of crystal growth in barite

Cited by 218 publications

References 11 publications

Structure of Barite (001)− and (210)−Water Interfaces

Structure of Barite (001)− and (210)−Water Interfaces

Illusory spirals and loops in crystal growth

Nucleation, Growth, and Aggregation of Mineral Phases: Mechanisms and Kinetic Controls

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