First-principles calculation studies on cesium in environmental situations; Hydration structures and adsorption on clay minerals

Machida, Masahiko  ; Okumura, Masahiko   ; Nakamura, Hiroki  ; Sakuramoto, Kazuhiro*

In order to clarify physicochemical behaviors of radioactive Cs released into environment from the Fukushima Daiichi Nuclear Power Plants, we study on two issues, i.e., hydration structures of Cs and its adsorption on a specific edge in a clay particle (mica) by employing first principles calculations. In this paper, firstly, we report on hydration structures of Cs by using Born-Oppenheimer first-principles molecular dynamics. Our striking finding in the hydration structures is that Cs has no clear second hydration shell in contrast to any other alkali cations. Secondly, we construct a model of the Frayed Edge Site and confirm that the model actually becomes selective for Cs when expanding the interlayer distance from that of the original crystal structure through the calculation of the ion-exchange energy.