Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies

Anniina Seppälä (Corresponding Author), Eini Puhakka, Markus Olin

    Research output: Contribution to journalArticleScientificpeer-review

    16 Citations (Scopus)

    Abstract

    The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (-1.0, -0.66 and -0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the self-diffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.
    Original languageEnglish
    Pages (from-to)197-211
    JournalClay Minerals
    Volume51
    Issue number2
    DOIs
    Publication statusPublished - 2016
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    swelling
    Density functional theory
    Swelling
    Molecular dynamics
    Crystalline materials
    Bentonite
    Cations
    montmorillonite
    cation
    Catalytic cracking
    Water
    Hydrocarbons
    Water content
    effect
    ion exchange
    Nanocomposites
    substitution
    Substitution reactions
    water content
    hydrocarbon

    Keywords

    • molecular dynamics
    • density functional theory
    • layer charge
    • montmorillonite
    • swelling
    • diffusion

    Cite this

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    title = "Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies",
    abstract = "The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (-1.0, -0.66 and -0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the self-diffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.",
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    author = "Anniina Sepp{\"a}l{\"a} and Eini Puhakka and Markus Olin",
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    Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies. / Seppälä, Anniina (Corresponding Author); Puhakka, Eini; Olin, Markus.

    In: Clay Minerals, Vol. 51, No. 2, 2016, p. 197-211.

    Research output: Contribution to journalArticleScientificpeer-review

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    AU - Seppälä, Anniina

    AU - Puhakka, Eini

    AU - Olin, Markus

    PY - 2016

    Y1 - 2016

    N2 - The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (-1.0, -0.66 and -0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the self-diffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.

    AB - The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (-1.0, -0.66 and -0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the self-diffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.

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