NONLINEAR VIBRATIONAL DYNAMICS OF A NEON ATOM IN C-60

Molecular dynamics simulations are performed for the endohedral Ne@C60 molecule. The principal focus of this research is to characterize the vibrational dynamics of the trapped Ne atom in the C60 cage. Empirical potentials are employed to describe the neon-carbon and carbon-carbon interactions. The Ne dynamics is analyzed by inspection of the trajectories and by calculating various distribution and time correlation functions. The nonlinear vibrational frequency of Ne is around 90 cm-1 at room temperature. The preferred location of the caged atom and time correlation functions of its position and angular momentum are discussed. Relaxation times are on the order of a few picoseconds, and one rinds that the Ne atom exhibits irregular, "chaotic" motion in the flexible cage at 300 K. This stochastic motion is thought to be driven, in part, by a nonlinear resonance between the Ne vibration and one or more of the cage vibrational normal modes. For comparison, the same neon initial conditions also produce a stochastic motion within a disordered, but rigid, cage; however, they lead to a regular, classical motion in the perfect icosohedral cage.