A comparative study of density functional and density functional tight   binding calculations of defects in graphene
  The density functional tight binding approach (DFTB) is well adapted for the study of point and line defects in graphene based systems. After briefly reviewing the use of DFTB in this area, we present a comparative study of defect structures, energies and dynamics between DFTB results obtained using the dftb+ code, and density functional results using the localised Gaussian orbital code, AIMPRO. DFTB accurately reproduces structures and energies for a range of point defect structures such as vacancies and Stone-Wales defects in graphene, as well as various unfunctionalised and hydroxylated graphene sheet edges. Migration barriers for the vacancy and Stone-Wales defect formation barriers are accurately reproduced using a nudged elastic band approach. Finally we explore the potential for dynamic defect simulations using DFTB, taking as an example electron irradiation damage in graphene. 
Alberto Zobelli, Viktoria V. Ivanovskaya, Philipp Wagner, Irene   Suarez-Martinez, Abu Yaya, Chris P. Ewels
cond-mat.mtrl-sci cond-mat.mes-hall