Potential negative friction coefficient predicted by first-principles calculations: A possible consequence of inaccurate computational models

The groundbreaking discovery of a negative friction coefficient (NCOF) challenges the long-held classic Amonton's law, ushering in fresh perspectives for comprehending and manipulating friction. Nevertheless, contradictory results about the NCOF have been recently reported by static first-principles calculations, which could foster misconceptions regarding the fundamental physics underlying this intriguing phenomenon. Here, we identify that disparities in computational models used in static friction calculations serve as the pivotal factor causing these inconsistencies through meticulous reproduction and comparison of the contradictory results. Specifically, the NCOF predicted by static first-principles in two-dimensional lamellar materials result from the overlooking of the pivotal role of the work done by the load during sliding. We further verify the indispensability of the work done by the load through theoretically scrutinizing the sliding process under constant load and under constant distance. Our findings propose a correct way for computing friction forces with static simulations, thereby advancing the scientific understanding and practical applications of frictional behavior in various materials systems.