|
چکیده
|
The oscillatory motion of fullerenes through graphene nanopores has recently attracted attention for its potential in high-frequency nano-oscillators, yet the roles of molecular flexibility, nanoscale energy dissipation, and model dependency remain insufficiently understood. This study investigates nano-oscillators formed by spherical fullerenes (C20, C40, C60, and C80) oscillating through a porous graphene sheet using molecular dynamics (MD) simulations and a continuum-based model. Interatomic interactions are modeled using Lennard-Jones (LJ) and Tersoff-Brenner (TB) potentials, where LJ is used in the continuum model and both LJ and TB are used in the MD simulations. For C60, the continuum model demonstrates good agreement with rigid and flexible MD simulations in terms of force, displacement, and velocity. The flexible MD model shows stronger oscillation damping due to nanoscale energy dissipation from internal vibrational modes, effects that are absent in the rigid model. As the graphene pore radius increases, the sensitivity of the oscillation frequency to molecular flexibility gradually decreases. The dynamic response of the nano-oscillator is found to depend strongly on geometrical parameters (fullerene size and pore radius) as well as initial conditions (inclination angle, initial offset, and initial velocity). The predicted oscillation frequencies lie in the gigahertz (GHz) range, with smaller fullerenes producing higher frequencies. Comparison of escape velocities indicates that heavier fullerenes lose oscillatory stability at lower velocities. The escape velocity of C60 is predicted to be 304.2 m/s by the continuum model and 237 m/s by the rigid MD simulation, while the flexible MD model yields a higher value of 323 m/s due to internal vibrational modes. These findings provide insight into the role of molecular flexibility and nanoscale dissipation in graphene-based nano-oscillators and may contribute to the design of high-frequency nanoelectromechanical systems (NEMS) with potential applications in energy harvesting and ultra-low-power sensing technologies.
|