Nanoscale simulation of Na-Montmorillonite hydrate under basin conditions, application of CLAYFF force field in parallel GCMC

Shahriyari, R.; Khosravi, Arash; Ahmadzadeh, A.

doi:10.1080/00268976.2013.772666

Cited by 36 publications

(21 citation statements)

References 62 publications

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“…The molecular simulation method used in this study is useful and has several advantages [1,2,3]. Not only can it simulate the molecular structure of the material [4], it can also simulate the dynamic change of molecules [5,6], intuitively describe the mechanism of the chemical reaction at the molecular and atomic scale, and verify the rationality of conclusions or predict the results of experiments [7,8]. Therefore, many scholars have also used the molecular simulation method to study the hydration properties of montmorillonite [9].…”

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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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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“…Compared with the traditional experimental research methods, the advantages of computer molecular simulation are obvious, which can not only simulate the molecular structure of the substance itself, but also simulate the dynamic change of the molecule when the substance reacts. It can visually describe the mechanism of reaction between substances at the molecular and atomic scales, and then verify the rationality of the experiment or predict the experimental results [13]. Skipper et al first simulated the interlayer water structure of Na-montmorillonite and Mg-montmorillonite by using Monte Carlo (MC) and molecular dynamics methods (MD) in 1991, and proposed a complete MC simulation method for a clay–ion–water system in 1995, including the construction of the model, the selection of potential functions, and the processing of non-bonded interaction, which laid the foundation for the future molecular simulation study of montmorillonite [14,15].…”

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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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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“…1,23 The high adsorption at low pH is usually 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 attributed to the presence of the fully protonated TC molecule, which is positively charged and adsorbs by cation exchange. Only a few ab initio studies have considered the smectites hydrated phases. [24][25][26][27][28][29][30][31][32] Berghout et al 13 The aim of the present work is to study by means of theoretical calculations the adsorption process of the fully protonated TC using Na-MMT as an adsorbent. DFT calculations are performed and geometric, electronic and magnetic properties are analyzed.…”

Section: Introductionmentioning

confidence: 99%

Geometrical and Electronic Properties of Hydrated Sodium Montmorillonite and Tetracycline Montmorillonite from DFT Calculations

et al. 2015

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The adsorption of fully protonated tetracycline (TC) using Na-montmorillonite (Na-MMT) as an adsorbent is studied by DFT calculations. Geometric, electronic and magnetic properties are analyzed. To the best of our knowledge, this is the first theoretical DFT research about Na-MMT as an adsorbent of TC cationic specie. Two Na-MMT models are considered: dry and hydrated Na-MMT. The incorporation of four water molecules in the interlayer space results in the expansion of the d 001 parameter from 10.13 Å (dry) to 12.85 Å (hydrated). Finally, when TC molecule is adsorbed in the basal space of MMT, the increment of the d 001 parameter is about 10 Å respect to hydrated model. Dry and hydrated Na-MMT present a non-magnetic (µ = 0 µ B ) and semiconductor behavior. Nevertheless, the TC-MMT system becomes conductor, and presents a very important magnetic moment (µ = 10.60 µ B ). After TC adsorption in MMT a potential valley with a slight depth in the MMT interlayer is generated. For this reason, it is proposed that TC adsorption would provide active sites for the adsorption of new species (like Na ions and water molecules).

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Nanoscale simulation of Na-Montmorillonite hydrate under basin conditions, application of CLAYFF force field in parallel GCMC

Cited by 36 publications

References 62 publications

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

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

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

Geometrical and Electronic Properties of Hydrated Sodium Montmorillonite and Tetracycline Montmorillonite from DFT Calculations

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