Simulation studies of proton transfer in N2H7+ cluster by classical ab initio Monte Carlo and quantum wave packet dynamics

The quantum effects on the proton-transfer reaction in the N2H7+ cluster ha s been studied using the classical ab initio Monte Carlo method and a one-d imensional model for the quantum wave packet dynamics on the ab initio MP2/ 6-31 + G* potential energy surface. The optimized stable structure has C-3v symmetry, in which the proton is bound to one NH3 molecule in such a way t hat the proton feels bistable potential. In contrast, we found that the pro ton was located at the center of two NH3 molecules with D-3d symmetry due t o the quantum effects of the proton kinetics. ne quantum simulations indica te that the reason the experimental spectra predict N2H7+ to have a symmetr ic D-3d Structure, contrary to the ab initio results, is that the quantum e ffects of the proton motion is completely neglected in the previous theoret ical calculations. The vibrational frequency for the N-H stretching mode wh ich corresponds to the proton transfer is estimated to be 706.7 cm(-1) by i ncluding proton quantum effects in contrast with 2100.1 cm(-1) obtained by the conventional ab initio MO method for the C-3v structure.