In the absence of electron-electron interactions, the energy dispersion of graphene was calculated under tension using the tight-binding approach and linear elasticity theory. The results show that tension strain along the zigzag direction can generate a gap for graphene, however, this gap is critical, requiring threshold deformations excess 24.5%. Tension strain along the armchair direction never generates a gap. The gap results from the merging of the two nonequivalent Dirac points in BZ. For strain along the armchair direction, the nonequivalent Dirac points move in opposite directions and ...
