Convergence of alkaline earth and transition metal oxide nanotube properties toward the 2D slab limit, computational investigation for energy conversion implications

Abstract

Nanoscale devices developed from low-dimensional materials (one and two-dimensional systems) have recently attracted great attention due to their critical applications in micro/nano electromechanics. However, the practical fabrication of 2D systems is often more challenging than that of their 1D counterparts. In the current investigation, the convergence of 1D nanotube properties toward the 2D slab limit has been verified and confirmed. In this regard, a variety of geometrical, electronic, and response (mechanical and piezoelectric) properties are computed for both zigzag (n,0) metal oxide MO (M = Be, Mg, Ca, Zn, Cd) nanotubes and MO 2D surfaces. The variation of such properties as a function of the tube index n (ranging from 6 to 48, corresponding to 24 to 192 atoms per cell, respectively) is highlighted. Additionally, the electronic and nuclear contributions to all aforementioned response properties have been discussed and analyzed. Interestingly, CdO (48,0) nanotube introduces considerable direct and converse piezoelectric constants: e11 = 6.04 |e|×bohr and d11 = 22.88 pm/V. These electromechanical coefficients converge well to the values of the 2D surface, while the response is entirely dominated by the ionic contribution, confirming the flexibility and softness. Such findings make these MO nanotubes good candidates for nanoscale energy conversion piezoelectric applications.