  Topological defects in graphene, dislocations and grain boundaries, are still
not well understood despites the considerable number of experimental
observations. We introduce a general approach for constructing dislocations in
graphene characterized by arbitrary Burgers vectors as well as grain
boundaries, covering the whole range of possible misorientation angles. By
using ab initio calculations we investigate thermodynamic and electronic
properties of these topological defects, finding energetically favorable
symmetric large-angle grain boundaries, strong tendency towards out-of-plane
deformation in the small-angle regimes, and pronounced effects on the
electronic structure. The present results show that dislocations and grain
boundaries are important intrinsic defects in graphene which may be used for
engineering graphene-based nanomaterials and functional devices.
