Communication: hydration structure and polarization of heavy alkali ions: a first principles molecular dynamics study of Rb+ and Cs+.

Hydration structure and polarization of Rb(+) and Cs(+) in liquid water at ambient conditions were studied by first principles molecular dynamics. Our systematic analysis of the relevant electronic structures, based on maximally localized Wannier functions, revealed that the dipole moment of H(2)O molecules in the first solvation shell of the ions slightly increases with increasing the atomic number. We also found that the polarization of heavy alkali ions, particularly Cs(+), tends to stabilize a peculiar asymmetric hydration structure with relevant consequences in the extraction of the harmful (137)Cs resulting from nuclear wastes.