Influence of screw dislocations on stacking order in graphite

This work examines how screw dislocations disrupt ideal stacking in graphenic materials, using a machine learning interatomic potential to model screw dislocation dipoles within different periodic cells. A novel tool is developed to assess local interlayer registration to quantify and visualise regions exhibiting stacking order. Using molecular dynamics simulations, we demonstrate that single screws exhibit greater stability in rhombohedral stacking compared to AA stacking, whereas double screws exhibit greater stability in Bernal AB stacking. The investigation reveals several mechanisms through which the ideal stacking configuration is achieved despite the presence of screw dislocations, including shearing, bond length distortion, and buckling. Furthermore, an upper threshold for the density of screw dislocations is calculated, beyond which ideal stacking cannot be realised, potentially offering an explanation for certain forms of turbostratic carbon. The findings also indicate that single screw dislocations hinder Bernal AB stacking in graphite, whereas double screw dislocations support Bernal stacking, which is significant for understanding the formation processes of graphite. • Single screws are stable in ABC graphite, double screws stable in AB graphite. • Above critical screw density graphite becomes buckled, turbostratic. • New code quantifies stacking registration quality and type in graphenic materials. • Machine-learning interatomic potentials benchmarked for stacking in graphite.