Mechanical, electronic and stability properties of multi-walled beryllium oxide nanotubes and nanopeapods: a density functional theory study

Single-, double-, and triple-walled beryllium oxide nanotubes (BeONTs) along with BeO nanopeapods were simulated and geometrically optimized under the density functional theory (DFT) framework to investigate their Young's modulus, electronic properties, and stability. We found better properties in single-walled nanotubes, either their electronic or mechanical properties, than other mentioned nanotubes. Increase in the radius and inter-wall distance made an overall decrease in the Young's modulus of SW and DW BeONTs. The highest obtained modulus of SWBeONTs and DWBeONTS was calculated for structures (14,0) and (8,0)@(14,0) with the magnitudes of 700.12 Gpa and 712.24 Gpa, respectively. In addition, increasing the wall number from one to two resulted to significant growth in Young's modulus of DWBeONTs while created no significant difference between DWBeONTs and TWBeONTs. Bandgap energy of single-walled nanotubes was higher than those of double- and triple-walled nanotubes, and the bandgap showed consistent soar in both SW and DW BeONTs via increase in the radius and inter-wall distance, respectively. Furthermore, considering nanopeapods with various interlayer distances revealed that the Young's modulus and energy gap behavior of these structures were similar to what we observed in SWBeONTs. However, nanopeapods showed weaker mechanical and semiconducting properties compared with SWBeONTs. Moreover, calculating the formation energies of all under consideration structures revealed a reduction of formation energy via an increase in the dimension of single-walled nanotubes, an increase in the dimension of nanotubes via adding more walls, and an increase in the dimension of peapod structures as well, and the bigger structures are more stable than smaller ones.