  Incomplete stacking dislocations are predicted to form at edges of the
shorter upper layer in two-dimensional hexagonal bilayers upon stretching the
longer bottom layer. A concept of the edge Burgers vector is introduced to
describe such dislocations by analogy with the Burgers vector of standard bulk
dislocations. Analytical solutions for the structure and energy of edge
stacking dislocations in bilayer graphene are obtained depending on the
magnitude of elongation and angles between the edge Burgers vector, direction
of elongation and edge. The barrier for penetration of stacking dislocations
inside the bilayer is estimated. The possibilities to measure the barrier to
relative motion of graphene layers and strain of graphene on a substrate by
observation of edge stacking dislocations are discussed.
