Monte Carlo molecular simulation of the Na-, Mg-, and mixtures of Na/Mg-montmorillonites systems, in function of the pressure

Miranda-Pascual, M.G.; Chavez-Garcia, M. L.

doi:10.1080/00268976.2014.983198

Cited by 12 publications

(7 citation statements)

References 48 publications

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“…According to Table 1 and Table 2, the semi-unit crystal structure formula of montmorillonite was assumed to be M x+y (Al 2-x Mg x )(Si 4-y Al y )O 10 (OH) 2 nH 2 O, where M is the exchangeable cations distributed between the montmorillonite layers(Ca 2+ ), and x+y is the semi-unit layer charge density. The structure belongs to the monoclinic C2/m space group, the crystal layer is constant: a = 0.523 nm, b = 0.906 nm, and the c value is variable [19,30] when the structural unit layer is anhydrous, c = 0.960 nm; and if there are water molecules existing between the layers, the c value will vary with the amount of water molecules and the type of exchangeable cations between layers. Table 3 is the atomic coordinates of montmorillonite in the three-dimensional model.…”

Section: Methodsmentioning

confidence: 99%

“…At present, molecular simulation technology has been successfully used to study the hydration characteristics of montmorillonite. Marry and Mignon studied the behavioral characteristics of different cations (Li + , Na + , and K + ) in the hydration process of montmorillonite by methods of MC and MD simulation, and found that as the water content between the smectite layers increased, Li + and Na + were easily separated from the montmorillonite interlayer, while K + moved to the surface of the siloxane tetrahedron and was bound to the surface [17,18,19]. Rahromostaqim compared the hydration and expansion properties of illite-montmorillonite (I-MMT) and Na-montmorillonite using molecular dynamics simulation, and found that at low CO 2 concentrations in Na-MMT, which has its layers’ charge concentrated in its octahedral sheet, weak ion-surface interactions result in fully hydrated ions and, therefore, more extensive swelling than in I-MMT [20].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Layer Charge Density on Hydration Properties of Montmorillonite: Molecular Dynamics Simulation and Experimental Study

Qiu

et al. 2019

IJMS

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Four kinds of Ca-montmorillonite with different layer charge density were used to study the effect of charge density on their hydration properties by molecular dynamics simulation and experiments. The research results of Z-density distribution of water molecules, Hw (hydrogen in water molecules), and Ca in the interlayer of montmorillonite show that the hydration properties of montmorillonite are closely related to its layer charge density. If the charge density is low, the water molecules in the interlayers are mainly concentrated on the sides of the central axis about –1.3 Å and 1.5 Å. As the charge density increases from 0.38semi-cell to 0.69semi-cell, the water molecules are distributed −2.5 Å and 2.4 Å away from the siloxane surface (Si-O), the concentration of water molecules near the central axis decreases, and at the same time, Ca2+ appears to gradually shift from the vicinity of the central axis to the Si-O surface on both sides in the montmorillonite layer. The simulation results of the radial distribution function (RDF) of the Ca-Hw, Ca-Ow (oxygen in water molecules), and Ca-Ot (the oxygen in the tetrahedron) show that the Ca2+ and Ow are more tightly packed together than that of Hw; with the increase of the charge density, due to the fact that the negative charge sites on the Si-O surface increase, under the action of electrostatic attraction, some of the Ca2+ are pulled towards the Si-O surface, which is more obvious when the layer charge density of the montmorillonite is higher. The results of the RDF of the Ot-Hw show that with the increase of charge density, the number of hydrogen bonds formed by Ot and Hw in the interlayers increase, and under the action of hydrogen bonding force, the water molecules near the central axis are pulled towards the two sides of Si-O surface. As a result, the arrangement of water molecules is more compact, and the structure is obvious. Correspondingly, the self-diffusion coefficient shows that the higher the layer charge density, the lower the self-diffusion coefficient of water molecules in interlayers is and the worse the hydration performance of montmorillonite. The experimental results of the experiments fit well with the above simulation results.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Layer Charge Density on Hydration Properties of Montmorillonite: Molecular Dynamics Simulation and Experimental Study

Qiu

et al. 2019

IJMS

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“…The result showed that calculated activation energies for ion and water diffusion in Na-montmorillonite were similar to each other and to the water hydrogen bond energy, suggesting the breaking of water–water and water-clay hydrogen bonds as a likely mechanism for interlayer diffusion [3]. Miranda-Pascuala used the Monte Carlo method to intensively study the expansion characteristics of Na-MMT, Mg-MMT, and Na/Mg-MMT, and found that when there were multiple cations existing in the interlayer of montmorillonite, the properties of montmorillonite mainly depended on the cations with the highest content in the interlayer of montmorillonite [17]. Zhang et al used molecular dynamics simulations to investigate the swelling properties, hydration behaviors, and mobility of the interlayer species of (Nax, Cay)-montmorillonites with different water contents.…”

Section: Introductionmentioning

confidence: 99%

“…In the mechanism of the influence of ions on the hydration characteristics in montmorillonite interlayers, most researchers believe that montmorillonite has high swelling capacity and hydrophilicity when montmorillonite layers contain cations with strong hydration ability (such as Na + and Li + ) [3,17,19,20]. Mary and Mignon used the Monte Carlo method and the molecular dynamics method to study the behavioral characteristics of different cations (Li + , Na + , and K + ) in the process of montmorillonite hydration, and found that with the increasing of the montmorillonite interlayer water content, Na + and Li + were easy to separate from the interlayer of montmorillonite, while K + would move and be bound to the silicon oxygen tetrahedron surface [21,22].…”

Section: Introductionmentioning

confidence: 99%

Effect of Layer Charge Characteristics on the Distribution Characteristics of H2O and Ca2+ in Ca-Montmorillonites Interlayer Space: Molecular Dynamics Simulation

Qiu

Liu

et al. 2019

Materials

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The charge characteristics of montmorillonite have significant effects on its hydration and application performances. In this study, a molecular dynamics simulation method was used to study the influence of the charge position and charge density of montmorillonite on the distribution of H2O and Ca2+ in layers. The results showed that when the layer charge is mainly derived from the substitution among ions in the tetrahedron, a large number of Hw and Ot are combined into a hydrogen bond in the interlayer, thus the water molecules are more compactly arranged and the diffusion of water molecules among the layers is reduced. In addition, the Ca2+ are diffused to the sides by a concentrated distribution in the central axis of the layer. As the charge density of the montmorillonite increases, the polarity of the Si–O surface increases, which lesds to the deterioration of the diffusibility of the water molecules and the structure of the water molecules in the interlayers is more stable. The increase in the layer charge density lesds to the expansion of the isomorphic substitution range of the crystal structure, which results in a more dispersed distribution of Ca2+ among the layers under the action of electrostatic attraction between the substituted negative sites and the Ca2+.

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“…According to the simulation results, we can further prove the rationality of conclusions and predict the experimental results. [2,21,22] Up to now, molecular simulation methods have been successfully used in the study of MMT and achieved many amazing research results, [14,23,24] such as the distribution and hydration characteristics of inorganic cation in MMT interlayers, [25][26][27][28] the distribution and kinetic characteristics of various kinds of atoms in organic modifiers and the arrangement of the organic modifiers in MMT interlayers. [29][30][31][32] At present, the research on organic MMT by molecular simulation mainly focuses on the effect of carbon chain length and the amount of modifier on the structure of organic MMT and the arrangement of organic modifier in MMT interlayers.…”

Section: Introductionmentioning

confidence: 99%

Microscopic Distribution of Chemical Constituents in the Interlayer Space of OTAC Intercalated Montmorillonite Complex:Molecular Simulation Study

et al. 2020

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This work employs molecular simulation to study the microscopic distribution of chemical constituents in the interlayer of octadecyl trimethyl ammonium chloride (OTAC) intercalated montmorillonite (MMT) complex. The results show that in the anhydrous MMT interlayers, the atoms of Co, Ho and No (C, H and N in OTAC) change from double‐layer to uneven multi‐layer distribution as the charge density of MMT increases, Ot (O in tetrahedron sheets) and No coordinate at the distance of 4.5 Å, the position of Co and Ho are closer to the siloxane surfaces than that of No, and the diffusivity of them decreases with the increase of charge density. In the hydrous MMT interlayers, the atoms of Co, Ho and No distribute in multiple layers along Z‐axis, the diffusivity of No is higher than that in the absence of water, but as for Co and Ho, only when charge density of MMT is low, the diffusivity of them is higher than that in the absence of water, and OTAC exhibit obvious three‐four‐five layers and six inclined layers arrangement between MMT layers with the increase of charge density.

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Monte Carlo molecular simulation of the Na-, Mg-, and mixtures of Na/Mg-montmorillonites systems, in function of the pressure

Cited by 12 publications

References 48 publications

Effect of Layer Charge Density on Hydration Properties of Montmorillonite: Molecular Dynamics Simulation and Experimental Study

Effect of Layer Charge Density on Hydration Properties of Montmorillonite: Molecular Dynamics Simulation and Experimental Study

Effect of Layer Charge Characteristics on the Distribution Characteristics of H2O and Ca2+ in Ca-Montmorillonites Interlayer Space: Molecular Dynamics Simulation

Microscopic Distribution of Chemical Constituents in the Interlayer Space of OTAC Intercalated Montmorillonite Complex:Molecular Simulation Study

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