Optimizing Structural and Mechanical Properties of Coiled Carbon Nanotubes with NSGA-II and Reactive Molecular Dynamics Simulation

Abstract

Coiled carbon nanotubes (CCNTs) have increasingly become a vital factor in the new generation of nanodevices and energy-absorbing materials due to their outstanding properties. Here, the multiobjective optimization of CCNTs is applied to assess their mechanical properties. The best trade-off between conflicting mechanical properties (e.g., yield stress and yield strain) is demonstrated and the optimization of the geometry enables us to find the astonishing CCNTs with a stretchability of 400%. These structures have been recognized for the first time in the field. We derived several highly accurate analytical equations for the yield stress and yield strain by the implementation of multiobjective optimization and fitting a theoretical model to the results of molecular dynamics (MD) simulations. The optimized structures are highly resilient because of two distinct deformation mechanisms depending on the dimensions of CCNTs. For small CCNTs, extraordinary extensibility is mainly contributed by buckling and nanohinge-like deformation with maintaining the inner coil diameter. On the other hand, for large CCNTs, this is accomplished by the creation of a straight CNT-like structure in the inner-edge of the CCNT with a helical graphene ribbon twisted around it. Our work represents an important advance in the design of CCNT based mechanical nanodevices.

Modeling and Analysis of the Geometry‐Dependent Mechanical and Thermal Properties of Coiled Carbon Nanotubes

“…All the atomic structures of coiled CNTs with various parameters via PFC modeling can be found at https://github.com/YanChen32/Coiled‐carbon‐nanotubes.git. Compared with previous works, [ 32,46 ] the atomic structures of coiled CNTs obtained by PFC modeling possess more perfect and smooth helical configurations, covering an arbitrary combination of geometrical parameters, i.e., CNT radius r , coil pitch l , and coil radius R , as shown in Figure 1c.…”

Unraveling the effect of hydrogenation on the mechanical properties of coiled carbon nanotubes: a molecular dynamics study

“…19,20 Chuang's model has been widely used in previous investigations to study mechanical properties. 21,[37][38][39]48,59 Based on this model, CCNTs contain non-hexagonal defects in the inner and outer parts of the coils, and the four fundamental parameters (s, n77, n75, and n55) determine the placement of these defects in the structures. In this way, placing heptagonal defects in the internal side and pentagonal defects in the external side of coils create concavity (negative curvatures) and convexity (positive curvatures) in the internal and external parts of CCNTs.…”

“…In addition, they reported that the yield stress and strain decrease with increasing temperature. In another research study, 39 they proposed several theoretical equations based on fitting a continuum model to MD simulation results. They illustrated that large CCNTs have relatively high amounts of yield point values compared to small CCNTs.…”

“…17,25 Today, they have found potential applications in biosensors, 22 nanoelectromechanical systems (NEMSs), 26 hydrogen storage, 27 and nanocomposites. [28][29][30] Until today, the outstanding mechanical properties of CCNTs are due to the combination of the extraordinary properties of CNTs and the capabilities that the helical morphology gives them, experimentally [31][32][33][34][35][36] and theoretically, 21,[37][38][39][40][41][42][43][44][45][46] have been reviewed.…”