Atomic-scale investigation of grain boundary motion in graphene

Grain boundaries (GBs) in graphene can migrate when irradiated by electron beams from a transmission electron microscope (TEM). Here, we present an ab initio study on the atomic scale mechanism for the GB motion with misorientation angle of 30° in graphene. From total energy calculations and energy barrier calculations, we find that a Stone--Wales(SW)-type transformation can occur more easily near GBs than in pristine graphene due to a reduced energy barrier. There are other cases of migration which can be understood by other type of transformation, named “evaporation of a carbon dimer”. We also find that a mismatch in the crystalline orientation at GBs can drive the evaporation of a carbon dimer easily by greatly reducing the corresponding overall energy barrier. After evaporation of the carbon dimer, the GBs can be stabilized through a series of SW-type transformations that result in GB motion. The GB motion induced by evaporation of the dimer is in excellent agreement with recent TEM experiments.