  We study heat transport across individual grain boundaries in suspended
monolayer graphene using extensive classical molecular dynamics (MD)
simulations. We construct bicrystalline graphene samples containing grain
boundaries with symmetric tilt angles using the two-dimensional phase field
crystal method and then relax the samples with MD. The corresponding Kapitza
resistances are then computed using nonequilibrium MD simulations. We find that
the Kapitza resistance depends strongly on the tilt angle and shows a clear
correlation with the average density of defects in a given grain boundary, but
is not strongly correlated with the grain boundary line tension. We also show
that quantum effects are significant in quantitative determination of the
Kapitza resistance by applying the mode-by-mode quantum correction to the
classical MD data. The corrected data are in good agreement with quantum
mechanical Landauer-B\"utticker calculations.
