Chaotic dynamics in small inert gas clusters: The influence of potential energy saddles

We have investigated the effect of potential energy saddles on the evolution of chaos in small (three- to seven-atom) inert gas clusters by comparing the local Kolmogorov entropy (K entropy) accumulated near a saddle with that accumulated in a potential well. We find that saddles which are relatively flat along the isomerization coordinate are most effective at reducing the local K entropy in the saddle region, indicating that these saddles tend to regularize the dynamics close to the saddle point. In three- and four-atom clusters, we also find that flat saddles decouple some or all of the cluster’s vibrational modes from one another; this leads to approximately quasiperiodic behavior in some degrees of freedom near the saddle regions of these clusters.