title: Characterizing molecular motion in H2O and H3O+ with dynamical instability statistics.
abstract: Sets of finite-time Lyapunov exponents characterize the stability and instability of classically chaotic dynamical trajectories. Here we show that their sample distributions can contain subpopulations identifying different types of dynamics. In small isolated molecules these dynamics correspond to distinct elementary motions, such as isomerizations. Exponents are calculated from constant total energy molecular dynamics simulations of H(2)O and H(3)O(+), modelled with a classical, reactive, all-atom potential. Over a range of total energy, exponent distributions for these systems reveal that phase space exploration is more chaotic near saddles corresponding to isomerization and less chaotic near potential energy minima. This finding contrasts with previous results for Lennard-Jones clusters, and is explained in terms of the potential energy landscape.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3100, USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Green
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hofer
authors.forename: R Stephen
authors.initials: RS
authors.lastname: Berry
authors.forename: David J
authors.initials: DJ
authors.lastname: Wales