Bond-order potential for the surface-terminated titanium carbide MXene monolayers Tin+1 CnTx (n=1,2, or 3;T=- O or - F)

Abstract

MXenes are an emerging family of two-dimensional (2D) materials with highly tunable properties. Their fundamental mechanical properties have received comparatively less research attention than other functional properties due to the difficulty of performing such experiments on 2D materials. Therefore, we have developed a bond-order potential for surface-terminated titanium carbide MXene monolayers (Tin+1CnTx, n=1,2,or3,T=-Oor-F), enabling large-scale atomistic simulations which can probe both mechanical properties and deformation mechanisms. The bond-order potential does an excellent job of capturing relevant structural, elastic, and defect properties of the studied MXenes with and without surface terminations and is computationally scalable to allow for molecular dynamics simulations of monolayers hundreds of nanometers in size, only an order of magnitude below typical monolayer experiments. Crucially, these large-scale simulations open the possibility to study more realistic MXenes containing distributions of both defects and nonuniform surface terminations. We demonstrate in this work that these variables can have significant effects on the mechanical response of MXenes and therefore offer additional property-tuning capabilities which can be utilized to inform synthesis and postprocessing techniques.