Influence of cutoff radius and tip atomic structure on energy barriers encountered during AFM tip sliding on 2D monolayers.

In computational studies using the Lennard-Jones (LJ) potential, the widely adopted 2.5cutoff radius effectively truncates pairwise interactions across diverse systems (Santra2008234704, Chen and Gao 2021502-12, Bolintineanu2014321-56, Takahiro and Kazuhiro 2010012123, Zhou2016718-26, Toxvaerd and Dyre 2011081102, Toxvaerd and Dyre 2011081102). Here, we assess its adequacy in determining energy barriers encountered by a Si monoatomic tip sliding on various two-dimensional (2D) monolayers, which is crucial for understanding nanoscale friction. Our findings emphasize the necessity of a cutoff radius of at least 3.5to achieve energy barrier values exceeding 95% accuracy across all studied 2D monolayers. Specifically, 3.5corresponds to 12.70 Å in graphene, 12.99 Å in MoSand 13.25 Å in MoSe. The barrier values calculated using this cutoff support previous experiments comparing friction between different orientations of graphene and between graphene and MoS(Almeida201631569, Zhang2014663-7). Furthermore, we demonstrate the applicability of the 3.5cutoff for graphene on an Au substrate and bilayer graphene. Additionally, we investigate how the atomic configuration of the tip influences the energy barrier, finding a nearly threefold increase in the barrier along the zigzag direction of graphene when using a Si(001) tip composed of seven Si atoms compared to a monoatomic Si tip.