▎ 摘　　要

This paper investigates strain effects on the electronic properties of single-layer and bilayer graphene using a first-principles method. The deformation significantly alters energy dispersion, band overlap, band gap, and the band edges of graphenes. Fermi velocity behaves both linearly and nonlinearly with the strains, depending on the types of deformation and the direction, of the Fermi velocity. In bilayer graphene, the uniaxial strain enhances the band overlap by 2 orders of magnitude. A semimetal-insulator transition occurs when bilayer graphene is under a compressive uniaxial strain along the zigzag chain direction. These strain-dependent results are useful for acquiring the intralayer and interlayer atomic relations or Slonczewski-Weiss-McClure, parameters. The intralayer coupling gamma(0) under the H-strain and interlayer couplings gamma(1), gamma(3), and gamma(4) under the P-strain decrease dramatically as the strain increases. Nevertheless, interlayer couplings vary more slowly with the H-strain than the P-strain.