Tetragraphene-Based Nanotubes Under Temperature Effects: Atomistic Insights into Nanostructural Degradation via Reactive Molecular Dynamics.

This research investigates the systematic nanomechanical behavior of tetragraphene-based nanotubes (TGCNTs) using classical molecular dynamics (CMD) simulations performed via the LAMMPS package with the reactive AIREBO-Morse potential. Tetragraphene is a novel carbon allotrope characterized by a unique mixture of sp2 and sp3 hybridization. We analyzed the nanomechanical properties of zigzag-like TGCNTs under uniaxial tensile loading, systematically examining the effects of chirality, diameter, length, and temperature ranging from 300 K to 2100 K, while maintaining a constant nanotube length. Our results reveal a distinct nanostructural degradation at high temperatures, where the nanotubes completely lose their structural stability above 1500 K. Under mechanical strain, the stress-strain curves highlight a strong dependence on chirality. The (0,n) TGCNTs exhibit brittle behavior, characterized by a short, nearly linear curve that terminates abruptly at a rapid fracture point without significant plastic deformation. In contrast, the (n,0) TGCNTs demonstrate remarkable ductility and irreversible plastic deformation flow. This is evidenced by a distinct plateau effect with constant stress up to 20% strain, followed by ultimate fracture at a strain over 40%, indicating a stress-induced structural phase transition. To map their transverse elasticity, Poisson's ratio (ν) was evaluated within the elastic regime, revealing an ultra-low value of ν=0.07 for the TGCNT (0,10) in close agreement with density functional theory (DFT) benchmarks, contrasting with an anomalously high value of ν=1.19 for the TGCNT (14,0) due to severe chiral anisotropy. The calculated Young modulus values range from 2379.90 to 3499.20 GPa.Å for (n,0) TGCNTs and 1886.70 to 2374.40 GPa.Å for (0,n) TGCNTs. These insights into the nanostructure-property relationships of TGCNTs provide essential design guidelines for their application in flexible electronics, nanocomposites, and advanced nanoelectromechanical systems (NEMSs).