  In this work, a combined modelling approach for crack propagation in
defective graphene is presented. Molecular dynamics (MD) simulations are used
to obtain material parameters (Young's modulus and Poisson ratio) and to
determine the energy contributions during the crack evolution. The elastic
properties are then applied in phase-field continuum simulations which are
based on the Griffith energy criterion for fracture. In particular, the
influence of point defects on elastic properties and the fracture toughness are
investigated. For the latter, we obtain values consistent with recent
experimental findings. Further, we discuss alternative definitions of an
effective fracture toughness, which accounts for the conditions of crack
propagation and establishes a link between dynamic, discrete and continuous,
quasi-static fracture processes on MD level and continuum level, respectively.
It is demonstrated that the combination of MD and phase-field simulations is a
well-founded approach to identify defect-dependent material parameters.
