A Concerted mechanism between proton transfer of Zundel anion and displacement of counter cation

Koizumi, Akihito*; Suzuki, Kimichi*; Shiga, Motoyuki   ; Tachikawa, Masanori*

path integral molecular dynamics simulation of MHO (M = Li, Na, and K) has been carried out to study how the structure and dynamics of low-barrier hydrogen-bonded Zundel anion, HO, can be affected by the counter alkali metal cation, M. Our simulation predicts that the quantum proton transfer in Zundel anion can be strongly coupled to the motion of counter cation located nearby. A smaller cation can induce larger structural distortion of the Zundel anion fragment making the proton transfer barrier higher, and hence lowers the vibration excitation energy. It is also argued that a large H/D isotope effect is present.