▎ 摘　　要

Exerting periodic potentials on graphene sheet may be realized by some techniques. Using T-matrix approach, the effect of a two-dimensional Kronig-Penney external periodic potential on the electronic states of graphene is studied. The energy band structure in honeycomb lattice of graphene in presence of a 2-D scalar potential is investigated. It is shown that this approach is an effective and more general one to obtain explicit form of dispersion relation. This expression of energy spectrum of graphene lattice can describe emergence of additional Dirac points.