Structural and Electronic Properties of Iron-Doped Sodium Montmorillonite Clays: A First-Principles DFT Study

• Autor(a) principal: Ferreira, Camila R. [UNESP]
• Data de Publicação: 2019
• Outros Autores: Pulcinelli, Sandra H. [UNESP], Scolfaro, Luisa, Borges, Pablo D.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1021/acsomega.9b00685; http://hdl.handle.net/11449/201192

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 G-point, while it is at V → G 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+). ©