Molecular Dynamics Simulations of a carbon nanotube based motor stimulated by an externally applied sinusoidally varying electric field

Molecular Dynamics simulations (MD) of a double walled carbon nanotube (DWNT) motor, consisting of two coaxial carbon nanotubes are performed, where the inner tube behaves as a ”shaft” and the outer one as a ”sleeve” [1]. Brenner potential [2] is used for the intratube interactions along with Nordlunds long range interaction term [3] to account for the intertube interactions. Unit positive and negative charges are attached to two diametrically opposite atoms of the shaft in this work. A sinusoidally varying electric field of amplitude 3×10 V/m and a frequency 2.045×10 rad/sec as used in [4] is applied to these two charged atoms to induce rotational motion in the system. We perform two sets of simulations. In the first set both the shaft and the sleeve are free to move as in [4]. Rotary behavior is observed for a very short period of time in this case which is accompanied by the usual pendulum like oscillations. In the second set of the simulations where the sleeve is held fixed, two locked states, not aligned along the direction of the applied electric field, are observed in the angular orientation of the shaft inside the fixed sleeve. The frequency of the shifts between these locked states correspond to the frequency of the applied electric field. These states are then explained in terms of the radial shape variations of the shaft mainly the changes in its potential energy surface (PES) and the centroid shifts inside the fixed sleeve. These locked states are significant from the point of view of application of carbon nanotubes as nanomotors. To overcome these locked states we explore a parameter space of the applied