Structural and Electronic Properties of Iron-Doped Sodium Montmorillonite Clays: A First-Principles DFT Study
Ferreira, Camila R.
Pulcinelli, Sandra H.
Scolfaro, Luisa M.
Borges, Pablo D.
American Chemical Society
First-principles calculations done via density functional theory were used to study the structural and electronic properties of sodium montmorillonite clay (Mt-Na+) of general formula MxAl3Si8O24H4Na·nH2O (Mx: Mg or Fe). The final position of the interlamellar sodium atom is found to be close to the oxygen atoms located on the upper surface of silica. Following Fe-Mt-Na+ system relaxation, with subsequent analysis of magnetic moment and magnetic states, the electroneutrality of the system established that both Fe2+ and Fe3+ oxidation states are possible to occur. The Mg2+-Mt-Na+ material shows a band gap energy greater than that of Fe2+-Mt-Na+ when iron is in the octahedral site. It is found that the valence-band maximum and the conduction-band minimum of iron-doped montmorillonite are both at the Γ-point, while it is at V → Γ for magnesium-doped montmorillonite. The calculated band gap from hybrid functional (HSE06) of Fe2+-Mt-Na+ is equal to 4.3 eV, exhibiting good agreement with experimental results obtained from ultraviolet-visible spectroscopy of the natural Mt-Na+ (Cloisite-Na+).
density functional theory, sodium montmorillonite clay, Physics
Ferreira, C. R., Pulcinelli, S. H., Scolfaro, L., & Borges, P. D. (2019). Structural and electronic properties of iron-doped sodium montmorillonite clays: A first-principles DFT study. ACS Omega, 4(11), pp. 14369–14377.
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