  Coiled Carbon Nanotubes (CCNTs) are increasingly set to become a vital factor
in the new generation of nanodevices and energy-absorbing materials due to
their outstanding properties. In the following work, the multi-objective
optimization of CCNTs is applied regarding their mechanical performances. Apart
from finding the best trade-off between conflicting mechanical properties (e.g.
yield stress and yield strain), the optimization enables us to find the
astonishing CCNTs concerning their stretchability. To the best of our
knowledge, these structures have not been recognized before, both
experimentally and computationally. Several highly accurate analytical
equations are derived by insights from the findings of multi-objective
optimization and fitting a theoretical model to the results of Molecular
Dynamics (MD) simulations. The structures resulted from optimizations 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, whereas 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. These findings would shed light on
the design of CCNT based mechanical nanodevices.
