Phase de Laves dans la première opale CT bidisperse

Gauthier, Jean-Pierre; Fritsch, Emmanuel; Aguilar-Reyes, Bertha Oliva; Barreau, A.; Lasnier, B.

doi:10.1016/j.crte.2003.11.005

Cited by 10 publications

(15 citation statements)

References 5 publications

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“…We thus find that crystallization can be enhanced by tuning the softness of the particle interactions, either by charge, ligands, or a stabilizer, in simulations or experiments. This finding is indeed consistent with the experimental observations of the LPs as they all seem to involve particles interacting with (slightly) soft repulsive interactions [3][4][5][6][7][8][9][10] . Moreover, introducing a small degree of softness in the particle interactions can be exploited in a wealth of other crystallization studies.…”

Section: Discussionsupporting

confidence: 90%

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Tuning the Glass Transition: Enhanced Crystallization of the Laves Phases in Nearly Hard Spheres

2020

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Section: Discussionsupporting

confidence: 90%

“…1). Experimentally, LPs have been observed in binary nanoparticle suspensions 3,4 , and in submicron-sized spheres interacting via soft repulsive potentials [5][6][7][8][9][10] .…”

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confidence: 99%

Tuning the Glass Transition: Enhanced Crystallization of the Laves Phases in Nearly Hard Spheres

2020

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“…Due to the small free energy difference, one expects to observe in experiments a mixture of all three Laves phases similar to the experimental observation of the randomhexagonal-close-packed ͑rhcp͒ crystals of pure hard spheres, which can be seen as a mixture of fcc and hcp crystals. It is interesting to note that the Laves phases have been observed in binary silicious opal with a diameter ratio of 0.76, 28 in agreement with our predictions. Fig.…”

Section: A Binary Mixtures Of Hard Spheressupporting

confidence: 89%

Stability of LS and LS2 crystal structures in binary mixtures of hard and charged spheres

Hynninen

Filion

Dijkstra

2009

The Journal of Chemical Physics

108

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We study by computer simulations the stability of various crystal structures in a binary mixture of large and small spheres interacting either with a hard sphere or a screened-Coulomb potential. In the case of hard-core systems, we consider structures that have atomic prototypes CrB, gammaCuTi, alphaIrV, HgBr2, AuTe2, Ag2Se and the Laves phases (MgCu2, MgNi2, and MgZn2) as well as a structure with space group symmetry 74. By utilizing Monte Carlo simulations to calculate Gibbs free energies, we determine composition versus pressure and constant volume phase diagrams for diameter ratios of q=0.74, 0.76, 0.8, 0.82, 0.84, and 0.85 for the small and large spheres. For diameter ratios 0.76 < or = q < or = 0.84, we find the Laves phases to be stable with respect to the other crystal structures that we considered and the fluid mixture. By extrapolating to the thermodynamic limit, we show that the MgZn2 structure is the most stable one of the Laves structures. We also calculate phase diagrams for equally and oppositely charged spheres for size ratio of 0.73 taking into consideration the Laves phases and CsCl. In the case of equally charged spheres, we find a pocket of stable Laves phases, while in the case of oppositely charged spheres, Laves phases are found to be metastable with respect to the CsCl and fluid phases.

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“…8) like those in many precious opals (e.g. Darragh et al, 1966;Sanders & Darragh, 1971;Gauthier et al, 2004). These areas grade into disorganized Opal-A to opal-CT transition 943 heterometric arrays of opal spheres in all directions ( Fig.…”

Section: Discussionmentioning

confidence: 96%

Microstructural changes accompanying the opal‐A to opal‐CT transition: new evidence from the siliceous sinters of Geysir, Haukadalur, Iceland

Jones¹,

Renaut

2007

Sedimentology

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Opaline silica (opal‐A) has formed in marine, lacustrine and geothermal environments throughout geological time. During diagenesis opal‐A normally changes to opal‐CT, then opal‐C, and finally to quartz. Such changes commonly destroy the original fabrics and any fossils that opal‐A contained. The physical changes that accompany the opal‐A to opal‐CT transition, however, are known poorly. X‐ray diffraction analyses, electron microprobe analyses and high‐resolution, high‐magnification scanning electron microscope imagery of siliceous sinters from the Geysir geothermal area in Iceland show that opal‐A is formed of heterometric arrays of randomly packed microspheres (up to 5 μm diameter) with neighbouring spheres commonly being joined by small connection pads. In contrast, enlarged spheres, lepispheres, inverse opal (two types) and spindle frameworks with hexagonal motifs characterize opal‐CT. The textures in opal‐CT, which vary on a microscale, reflect the complex interplay between dissolution (e.g. inverse opal) and precipitation (e.g. enlarged spheres, spindle frameworks) that probably was mediated by groundwater in a near‐surface environment. The processes deciphered from these young rocks should, however, be applicable to sedimentary opal‐A and opal‐CT of all ages, irrespective of their origin.

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Phase de Laves dans la première opale CT bidisperse

Cited by 10 publications

References 5 publications

Tuning the Glass Transition: Enhanced Crystallization of the Laves Phases in Nearly Hard Spheres

Tuning the Glass Transition: Enhanced Crystallization of the Laves Phases in Nearly Hard Spheres

Stability of LS and LS2 crystal structures in binary mixtures of hard and charged spheres

Microstructural changes accompanying the opal‐A to opal‐CT transition: new evidence from the siliceous sinters of Geysir, Haukadalur, Iceland

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