Convergence of Alkaline Earth and Transition Metal Oxide Nanotube Properties Toward the 2D Slab Limit, Computational Investigation for Energy Conversion Implications

Nanoscale devices developed from low dimensional materials (one and two dimensional systems)
have attracted recently great attention due to their critical applications in micro/nano
electromechanics. However, the pragmatic fabrication of the 2D systems is being, frequently,
more challenged rather the corresponding 1D ones. Hence, 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, where the variation of such properties as a function of the tube
index n; n ranging from 6 to 48 (24 to 192 atoms per cell, respectively), is highlighted. Additionally,
the electronic and the 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 jej bohr and d11 = 22.88 pm/V. These
electromechanical coefficients are converged so well to the values of the 2D surface, while
the response is entirely predominated by the ionic contribution confirming the flexibility and
softness. Such findings would make these MO nanotubes as good candidates for nanoscale
energy conversion piezoelectric applications.