Simulation of layered double hydroxide intercalates

Aicken, A. Michael; Bell, I. S.; Coveney, Peter V.; Jones, William

doi:10.1002/adma.19970090610

Cited by 56 publications

(48 citation statements)

References 13 publications

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“…The negative entropy observed for the Cl Ϫ -NO 3 Ϫ exchange is possibly due to the fact that the nitrate anion, which is forced to adopt an arrangement which favours the closest possible packing, loses most of its degrees of freedom upon intercalation: computational simulation of a layered double hydroxide of the type [Mg-Al-NO 3 ] has indeed shown that the nitrate anions must tilt away from coplanarity with the metal hydroxyl sheets in order to mimimize important steric repulsions, the layers then being pushed apart. 17 Of course, while the nitrate anions lose degrees of freedom upon intercalation, the expelled chloride anions gain mobility in the solvent. However, the fact that the entropy of exchange is negative seems to indicate that the former effect prevails over the latter.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamics of anion exchange on a chloride-intercalated zinc–aluminum layered double hydroxide: a microcalorimetric study

Israëli

Taviot-Guého

Besse

et al. 2000

J. Chem. Soc., Dalton Trans.

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The thermodynamic properties of anion exchange on a chloride-intercalated zinc-aluminium layered double hydroxide have been studied at 298.15 K. The heats for total exchange of Cl Ϫ for F Ϫ , Br Ϫ , I Ϫ , OH Ϫ , NO 3 Ϫ , and SO 4 2Ϫhave been determined by microcalorimetry and the standard molar enthalpies of these exchange reactions have been estimated. For the processes involving OH Ϫ and NO 3 Ϫ , the exchange isotherms have been determined using potentiometry in the former case and capillary ion analysis in the latter. The standard molar Gibbs free energy and entropy changes upon exchange of Cl Ϫ for OH Ϫ and exchange of Cl Ϫ for NO 3 Ϫ have been calculated as a function of the fraction of exchanged Cl Ϫ . These exchange processes appear to be entropy-driven, but the selectivity is controlled by the enthalpic contribution.

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Section: Resultsmentioning

confidence: 99%

Thermodynamics of anion exchange on a chloride-intercalated zinc–aluminum layered double hydroxide: a microcalorimetric study

Israëli

Taviot-Guého

Besse

et al. 2000

J. Chem. Soc., Dalton Trans.

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“…Most of this theoretical effort has examined the behavior of interlayer anions and hydration [34][35][36][79][80][81][82] and the intercalation of organic molecules. 83,84 A series of molecular dynamics simulations of the structure and hydration of hydrotalcite using CLAYFF was performed by Wang et al 79 The composition of the hydrotalcite corresponded to Mg 2 Al(OH) 6 Cl‚nH 2 O with chloride representing the interlayer anions. This stoichiometry results in an interlayer with a single chloride ion per aluminum with variable water solvating the chloride ion.…”

Section: Resultsmentioning

confidence: 99%

Molecular Models of Hydroxide, Oxyhydroxide, and Clay Phases and the Development of a General Force Field

2004

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The fate of chemical and radioactive wastes in the environment is related to the ability of natural phases to attenuate and immobilize contaminants through chemical sorption and precipitation processes. Our understanding of these complex processes at the atomic level is provided by a few experimental and analytical methods such as X-ray absorption and NMR spectroscopies. However, due to complexities in the structure and composition of clay and other hydrated minerals, and the inherent uncertainties of the experimental methods, it is important to apply theoretical molecular models for a fundamental atomic-level understanding, interpretation, and prediction of these phenomena. In this effort, we have developed a general force field, CLAYFF, suitable for the simulation of hydrated and multicomponent mineral systems and their interfaces with aqueous solutions. Interatomic potentials were derived from parametrizations incorporating structural and spectroscopic data for a variety of simple hydrated compounds. A flexible SPC-based water model is used to describe the water and hydroxyl behavior. Metal-oxygen interactions are described by a LennardJones function and a Coulombic term with partial charges derived by Mulliken and ESP analysis of DFT results. Bulk structures, relaxed surface structures, and intercalation processes are evaluated and compared to experimental and spectroscopic findings for validation. Our approach differs from most others in that we treat most interatomic interactions as nonbonded. This allows us to effectively use the force field for a wide variety of phases and to properly account for energy and momentum transfer between the fluid phase and the solid, while keeping the number of parameters small enough to allow modeling of relatively large and highly disordered systems. Simulations of clay, hydroxide, and oxyhydroxide phases and their interfaces with aqueous solutions combine energy minimization and molecular dynamics methods to describe the structure and behavior of water, hydroxyl, surface species, and intercalates in these systems. The results obtained to date demonstrate that CLAYFF shows good promise to evolve into a widely adaptable and broadly effective force field for molecular simulations of fluid interfaces with clays and other clay-related phases, as well as other inorganic materials characterized by complex, disordered, and often ill-determined structure and composition.

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“…Surface diffusion rates can be overestimated, and the structure of the water layers at the interface can be distorted. Studies modeling ionic complexes in clays and MMLHs with all atoms in the system movable are beginning to appear in the literature (Aicken et al, 1997;Teppen et al, 1997, Hartzell et al, 1998Williams et al, 1999), but to date these concern primarily questions of structure and swelling, and not the dynamics of interlayer and surface species.…”

Section: Introductionmentioning

confidence: 99%

Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel’s salt)

Kirkpatrick

Cygan

2000

American Mineralogist

105

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Simulation of layered double hydroxide intercalates

Cited by 56 publications

References 13 publications

Thermodynamics of anion exchange on a chloride-intercalated zinc–aluminum layered double hydroxide: a microcalorimetric study

Thermodynamics of anion exchange on a chloride-intercalated zinc–aluminum layered double hydroxide: a microcalorimetric study

Molecular Models of Hydroxide, Oxyhydroxide, and Clay Phases and the Development of a General Force Field

Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel’s salt)

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