LElTER TO THE EDITOR Local interpretation of chaotic dynamics in a many-body classical Hamiltonian system

Abstract. The Kolmagorov entropy of a model Ar, cluster converges smoothly to its limiting value when averages are taken over increasingly long segments of a molecular dynamics trajectory. We exploit this convergence and the analytical relation between the local Kolmogorov function and the potential energy surface to obtain a detailed understanding o f the classical dynamics of Ar,. In particular, we are able to explain why the Kolmogorov entropy increases steadily with the total energy and then reaches a plateau. Several generalizations regarding more complex molecular systems are inferred. Recent studies have focused upon the characterization of dynamical properties of Hamiltonian systems in terms of Liapunov exponents, Kolmogorov entropy (Kol-mogorov 1959) and fractal dimensions (Mandelbrot 1983). Sharp and broad peaks in the power spectra ofsuch systems have been related to the distribution of local Liapunov exponents in a Hamiltonian system with only two degrees of freedom (SepGlveda et a / 1988). However, the latter approach does not illuminate the results obtained by computer simulations (Beck et a / 1988) even for a system as simple as Ar,. Here we construct the Jacobian for the simplest propagator of the motion and consider th