Simulation Studies of Proton Transfer in N2H7+ Cluster by Classical ab Initio Monte Carlo and Quantum Wave Packet Dynamics

Abstract

The quantum effects on the proton-transfer reaction in the N2H7+ cluster has been studied using the classical ab initio Monte Carlo method and a one-dimensional model for the quantum wave packet dynamics on the ab initio MP2/6-31+G* potential energy surface. The optimized stable structure has C3v symmetry, in which the proton is bound to one NH3 molecule in such a way that the proton feels bistable potential. In contrast, we found that the proton was located at the center of two NH3 molecules with D3d symmetry due to the quantum effects of the proton kinetics. The quantum simulations indicate that the reason the experimental spectra predict N2H7+ to have a symmetric D3d structure, contrary to the ab initio results, is that the quantum effects of the proton motion is completely neglected in the previous theoretical calculations. The vibrational frequency for the N−H stretching mode which corresponds to the proton transfer is estimated to be 706.7 cm-1 by including proton quantum effects in contrast with 21...