Theoretical prediction of stress-induced phase transformations of the second kind in graphene

Simulations of planar graphene undergoing in-plane deformations are found to develop crystal structures different from the usual hexagonal configuration-either monoclinic or nearly orthorhombic-through two different types of solid phase transitions of the second kind. They are achieved through a concerted C-2 rotation similar in appearance to the onset of the Stone-Wales transformation. The key result is the observation of the early rotation in even the smallest primitive cell. In connection to earlier findings on reversibility, the thermodynamic or kinetic character of the rearrangement is found to depend on the macroscopic straining direction.