Gap effect on stable rotation of a carbon nanotube nearby diamond needles

A rotary nanomotor from carbon nanotube (CNT) and diamond is conceptually proposed, and the condition for stable rotation of the rotor is investigated. By putting several diamond needles (DNs) nearby a CNT, the tube can be driven to rotate at finite temperature. At finite temperature, thermal vibration of atoms in the CNT rotor and DNs leads to collision when their distance, i.e., Gap, is close to 0.34 nm, which is the equilibrium stance between neighbor sp(2) carbon nanostructures, e.g., graphene or CNT. The fixed DNs provide the rotor repulsion via their tip atoms during collision. If the repulsion can generate a torque moment with unchanged direction, the rotor will be accelerated to rotate. After a period of acceleration, the stable rotational frequency (SRF) of the rotor can be obtained when Gap is no more than 0.34 nm. Numerical results demonstrate that the rotational direction depends on the value of Gap when each DN has only one pair of tip atoms; the temperature has a significant effect on the value of SRF but little effect on the rotational direction; and the rotation of the rotor becomes unstable due to breakage of DNs when Gap is higher than 0.34 nm.