title: Characterization of Adsorbed Alkali Metal Ions in 2:1 Type Clay Minerals from First-Principles Metadynamics.
abstract: Adsorption states of alkali metal ions in three kinds of 2:1 type clay minerals are systematically investigated via first-principles-based metadynamics. Our reconstructed free energy surfaces in a two-dimensional space of coordination numbers specifically employed as collective variables for describing the interlayer cations show that an inner-sphere (IS) complex is preferentially formed for Cs(+) in the 2:1 type trioctahedral clay minerals with saponite-like compositions, where lighter alkali metal ions show a tendency to form an outer-sphere one instead. The strong preference for an IS complex observed for Cs(+) is found to result partially from the capability of recognizing selectively Cs(+) ions at the basal O atoms with the Lewis basicity significantly enhanced by the isomorphic substitution in tetrahedral sheets.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: §Fukushima Environmental Safety Center, Japan Atomic Energy Agency (JAEA), 6-6 Sakae-machi, Fukushima-shi, Fukushima 960-8031, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: §Fukushima Environmental Safety Center, Japan Atomic Energy Agency (JAEA), 6-6 Sakae-machi, Fukushima-shi, Fukushima 960-8031, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yaita