Structural properties and thermal stability of multi-walled black phosphorene nanotubes and their operation as temperature driven nanorotors

In this paper, we explore the influence of structural properties, thermal stability, and temperature on the rotational frequency of (0,n) armchair multi-walled black phosphorene nanotubes (MW beta PNTs). Using Density Functional Theory (DFT) calculations, we first determine the influence of the outer wall rotation on the structural stability of (0,12)@(0,19) DW beta PNTs, and (0,12)@(0,19)@(0,26) TW beta PNTs. The results indicate that the relative energies of the DW- and the TW beta PNTs do not change with the rotation angle. Therefore, the outer wall rotation is not important for the structural formation of the MW beta PNTs. Then, using molecular dynamics (MD) simulations, we study the structural properties, thermal stability, and rotational frequency of (0,12)@(0,19) DW beta PNTs, (0,12)@(0,19)@(0,26) TW beta PNTs, and (0,12)@(0,19)@(0,26)@(0,33) QW beta PNTs from 1 K to 400 K. The calorific curve, the mean-squared displacement, and the radial distribution function are analyzed to characterize the temperature behavior of the MW beta PNTs. In all cases, the nanotubes are rotating: they act as thermal-driven rotors as the temperature increases, with a maximum rotational frequency of 16.7 GHz (clockwise direction) at 5 K for the DW beta PNTs. Our results suggest that MW beta PNTs could be used to construct room temperature nanomotors.