Mechanical properties of single-walled penta-graphene-based nanotubes: A DFT and Classical molecular dynamics study

Highlights: • Mechanical properties of different penta-graphene nanotubes were provided. • One type of PGNT presents less total energy than that of penta-graphene sheet. • All PGNTs are auxetic, with Poisson's ratio values ranging from –0.02 to –0.33. • Existence of a transition from $\beta$ to $\alpha$ (n,n) PGNTs during tension and before fracture. • Values of PGNT Young's modulus range from 600 to 1000 GPa. Membranes of carbon allotropes comprised solely of densely packed pentagonal rings, known as penta-graphene, exhibit negative Poisson's ratio (auxetic behavior) and a bandgap of 3.2 eV. In this work, we investigated the structural stability, mechanical and fracture properties of nanotubes formed by rolling up penta-graphene membranes, the so-called penta-graphene nanotubes (PGNTs). Single-walled PGNT of three distinct configurations: $(n,0)$, and two types of $(n,n)$ (here called $\alpha$ and $\beta$) were studied combining first-principles calculations and reactive molecular dynamics simulations. Our results showed Young's modulus values of 680–800 GPa, critical strain of 18–21%, ultimate tensile stress of 85–110 GPa, and Poisson's ratio values ranging from $-0.05$ to $-0.30$ (auxetic behavior). During stretching at room temperature, we observed a transition from $\beta$-$(n,n)$ to $\alpha$-$(n,n)$ PGNT near the critical strain. Fracture of PGNTs starts at the bonds that are mostly aligned to the stretching direction and after nanotube radial collapse.