▎ 摘　　要

With molecular dynamics simulations, deformation and fracture processes in ultranarrow graphene nanoribbons are examined. It is revealed that twisted and flat graphene nanoribbons having width of 4 atomic cells exhibit giant plasticity specified by plastic strain degrees of approximate to 180% and approximate to 290%, respectively. Such extremely high strain values were never observed in previous experiments and simulations. Plastic deformation of the graphene nanoribbons occurs through generation and re-arrangement of disclinations (non-six membered rings of carbon atoms) as well as transformations of disclinated graphene regions into monatomic carbon chains. Complete failure of the ultranarrow graphene nanoribbons is realized through breaks of C-C interatomic bonds at monatomic carbon chains characterized by high tensile strength of approximate to 45-50 GPa.