• Application of localized reactivity index in combination with periodic DFT calculation to rationalize the swelling mechanism of clay type inorganic material

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      https://www.ias.ac.in/article/fulltext/jcsc/117/05/0533-0539

    • Keywords

       

      Localized reactivity index; periodic DFT calculations; swelling mechanism; inorganic clays; interlayer cations

    • Abstract

       

      Clays are layered alumino-silicates. Clays swell and expand in aqueous solution. This property governs the usage of these materials in synthesis of nano-composites and is a source of many of its catalytic applications. We used both localized and periodic calculations within the realm of density functional theory (DFT) on a series of monovalent (Li+, Na+, K+, Rb+, Cs+), and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations, to monitor their effect on the swelling of clays. The activity order obtained for the exchangeable cations among all the monovalent and divalent series studied is: Mg2+ > Ca2+ > Sr2+ > Ba2+ > Cs+ > Rb+ > Na+ > Li+ > K+. We have studied two types of clays, montmorillonite and beidellite, with different surface structures and with/without water using periodic calculations. We have calculated the layer spacing at the first, second and third hydration shells of exchangeable cation, to compare with the experimentald-spacing values to correlate with humidity. A novel quantitative scale is proposed in terms of the intermolecular relative nucleophilicity of the active cation sites in their hydrated state through Fukui functions using hard-soft acid base (HSAB) principle. Finally, a swelling mechanism is proposed. This is a unique study where a combination of periodic and localized calculations has been performed to validate the capability of reactivity index calculations in material designing.

    • Author Affiliations

       

      Abhijit Chatterjee1

      1. Accelrys K K, Nishishinbashi TS Bldg. 11F. 3-3-1 Nishishinbashi, Minato-ku, Tokyo - 105-0003, Japan
    • Dates

       
  • Journal of Chemical Sciences | News

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