Ab initio analysis of proton transfer dynamics in (H2O)(3)H+

We have harvested ab initio trajectories of proton transfer in (H2O)(3)H+ b y combining Car-Parrinello molecular dynamics (CPMD) with the transition pa th sampling method. Two transition state regions contribute to these dynami cs, with saddle points similar to those identified by Geissler, Dellago, an d Chandler for an empirical model of the same cluster [Phys. Chem. Chem. Ph ys, 1 (1999) 1317]. As in that model, the location of a transition state al ong a finite-temperature trajectory indicates that proton transfer is drive n by reorganization of the oxygen ring. From vibrational properties it is e stimated that the characteristic time for proton transfer is similar to 1 n s at a temperature of 300 K. (C) 2000 Elsevier Science B.V. All rights rese rved.