Study of top-quark pair modelling and uncertainties using ATLAS measurements at $\sqrt{s}$=13 TeV

The modelling of top-quark pair production by the ATLAS collaboration utilises recent Monte Carlo generators with next-to-leading order precision in QCD and matched to a parton shower. Various next-to-leading order and multileg generators and their settings are explored and their predictions are compared to recent ATLAS measurements in three different top-quark pair decay channels using an integrated luminosity of 36.1~\ifb of $\sqrt{s}=13$ TeV $pp$ collision data. The use of alternative generators and settings for the top-quark modelling uncertainty are explored, with particular focus on uncertainties related to the matching scale and algorithms, the parton shower, and the initial-state radiation.