Semiclassical chaos in atomic clusters: An exploration with ring-polymer molecular dynamics

The ring-polymer molecular dynamics (RPMD) method was recently shown to provide a powerful framework to address the time evolution of many-particle semiclassical systems. Its underlying Hamiltonian formulation is exploited here to define and compute some measures of deterministic chaos, namely the Lyapunov characteristic exponent. Applications are presented for weakly bound neon clusters, with the aim of assessing the influence of nuclear delocalization on the nonlinear dynamics. It is found that the balance between the additional degrees of freedom in the RPMD description and the harmonic nature of the additional interactions leads to more regular dynamics at high temperature, but more chaotic dynamics at low temperature. Intrinsic features of quantum effects on the isomerization dynamics also have a signature on the Lyapunov exponent.