In computational studies using the Lennard-Jones (LJ) potential, the widely adopted 2.5<i>σ</i>cutoff radius effectively truncates pairwise interactions across diverse systems (Santra<i>et al</i>2008<i>J. Chem. Phys.</i><b>129</b>234704, Chen and Gao 2021<i>Friction</i><b>9</b>502-12, Bolintineanu<i>et al</i>2014<i>Part. Mech.</i><b>1</b>321-56, Takahiro and Kazuhiro 2010<i>J. Phys.: Conf. Ser.</i><b>215</b>012123, Zhou<i>et al</i>2016<i>Fuel</i><b>180</b>718-26, Toxvaerd and Dyre 2011<i>J. Chem. Phys.</i><b>134</b>081102, Toxvaerd and Dyre 2011<i>J. Chem. Phys.</i><b>134</b>081102). 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 3.5<i>σ</i>to achieve energy barrier values exceeding 95% accuracy across all studied 2D monolayers. Specifically, 3.5<i>σ</i>corresponds to 12.70 Å in graphene, 12.99 Å in MoS₂and 13.25 Å in MoSe₂. The barrier values calculated using this cutoff support previous experiments comparing friction between different orientations of graphene and between graphene and MoS₂(Almeida<i>et al</i>2016<i>Sci. Rep.</i><b>6</b>31569, Zhang<i>et al</i>2014<i>Sci. China</i><b>57</b>663-7). Furthermore, we demonstrate the applicability of the 3.5<i>σ</i>cutoff 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.