Effect of solvent fluctuations on proton transfer dynamics:: a hybrid AM1/MM molecular dynamics simulation on the [H3N-H-NH3]+ system

Combined AM1/TIP3P Molecular Dynamics simulations have been carried out to investigate proton transfer dynamics in aqueous solution for the proton-bound ammonia dimer model system. The distance between nitrogen atoms has been fixed to 2.62 Angstrom so that proton transfer events occur every 10-20 ps in average. The chemical reaction is clearly shown to be preceded by a solvent fluctuation which starts about 700 fs before reaching the transition structure. (C) 1999 Elsevier Science B.V. All rights reserved.