Rotationally induced transitions in small clusters

Role of inertial forces on the chaotic dynamics of flexible rotating bodies

The nonlinear dynamics of isolated flexible but rotating many-body atomic systems is theoretically investigated, following the dependence on initial conditions through Lyapunov exponents. The tangent-space equations of motion that rule the time evolution of such small perturbations are rewritten in the rotating reference frame, and the various contributions of the centrifugal, Coriolis, and Euler forces are determined. Evaluating the largest Lyapunov in the rotating frame under various approximations, we show on the example of Lennard-Jones clusters that the dynamics in phase space is qualitatively at variance with the effective dynamics on the centrifugal energy surface. Coupling terms between positions and momenta in phase space, especially arising from the Coriolis force, are essential to recover the measure of chaos in the fixed reference frame.

Effective numbers of modes applied to analysis of internal dynamics of weakly bound clusters

The dependence of the volume of the chaotic component in the internal dynamics of triatomic van der Waals clusters on the angular momentum is calculated using the Monte Carlo and molecular dynamics methods. It has been found that this dependence is nonmonotonic and that its functional form varies for different values of the total energy. The effective number of rotational modes was used to clarify why a change in the volume of chaotic component of the phase space happens for certain values of the angular momentum. We conclude that a large fraction of regular trajectories in relation to all trajectories appears only when there is a possibility for the regular motion to perform a rotation different from that for a chaotic motion. When such difference is small, the regular motion disappears. The effective number of rotational modes can be used to estimate the difference in the type of rotation and is a convenient parameter which controls changes in the dynamics of the system.