  We extend the phase field crystal (PFC) framework to quantitative modeling of
polycrystalline graphene. PFC modeling is a powerful multiscale method for
finding the ground state configurations of large realistic samples that can be
further used to study their mechanical, thermal or electronic properties. By
fitting to quantum-mechanical density functional theory (DFT) calculations, we
show that the PFC approach is able to predict realistic formation energies and
defect structures of grain boundaries. We provide an in-depth comparison of the
formation energies between PFC, DFT and molecular dynamics (MD) calculations.
The DFT and MD calculations are initialized using atomic configurations
extracted from PFC ground states. Finally, we use the PFC approach to
explicitly construct large realistic polycrystalline samples and characterize
their properties using MD relaxation to demonstrate their quality.
