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The short‐range order of ions in clay minerals: Sm 3+ coordination
Author(s) -
Sobolev Oleg,
Cuello Gabriel J.,
Scheinost Andreas C.,
Johnson Mark R.,
Nikitenko Sergey,
Le Forestier Lydie,
Brendle Jocelyne,
Charlet Laurent
Publication year - 2011
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201000311
Subject(s) - coordination sphere , coordination number , extended x ray absorption fine structure , adsorption , montmorillonite , hectorite , chemistry , clay minerals , crystallography , quasielastic neutron scattering , ion , cationic polymerization , solvation shell , neutron diffraction , neutron scattering , molecule , chemical physics , scattering , crystal structure , absorption spectroscopy , inelastic neutron scattering , mineralogy , organic chemistry , solvation , physics , quantum mechanics , optics
Experimental techniques as neutron diffraction (ND) with isotopic substitution (NDIS), extended X‐ray absorption fine structure spectroscopy (EXAFS), and quasielastic neutron scattering (QENS), in combination with molecular dynamics (MD) simulations, are usually applied to the study of non‐crystalline solids, but they are also very useful for the study of complex systems, where the short range order provides an insight of its structure and dynamics. Here, they are used in the study of the coordination of the Sm 3+ in the interlayer of hydrated synthetic montmorillonite and hectorite. The ND results indicate that not all oxygen atoms in the first coordination shell of the Sm 3+ belong to water molecules, supporting the formation of the Sm 3+ inner‐sphere complex. On the other hand, the other techniques suggest that the adsorbed Sm 3+ cations form outer‐sphere complexes with the clay surface. The hypothesis making compatible all results is that there are different Sm species adsorbed in the clay interlayer: a part of Sm is in the Sm 3+ cationic form, forming outer‐sphere adsorption complexes, another part is hydrolyzed and present in the interlayer space as Sm(OH) 2+ , ${\rm Sm(OH)}_{2}^{ + } $ , or ${\rm Sm(OH)}_{3}^{0} $ species. The latter are more hydrophobic than Sm 3+ cations and can be dehydrated and are able to stick to the clay surface.