Polarizability in graphene increases nanoscale friction by amplifying interfacial energy corrugation

Early classical molecular dynamics simulations utilizing non-polarizable force fields estimated the water–graphene friction coefficient to be ∼1.4×104Nsm−3. However, recent studies have demonstrated that electric polarization and quantum effects beyond the Born–Oppenheimer approximation are crucial for accurately describing nanoscale friction. Observations from recent models suggest that incorporating electric polarization leads to higher predicted friction coefficients. This study evaluates the water–graphene friction coefficient using the SWM4-NDP polarizable water model interacting with both polarizable and non-polarizable graphene models. The friction coefficient is initially computed via equilibrium molecular dynamics (EMD) utilizing the Green–Kubo relation. Given the ongoing debate regarding the application of this methodology, the friction coefficient of the fully polarizable system is also evaluated using non-equilibrium molecular dynamics. Our EMD calculations show that incorporating explicit electric polarization in graphene increases the interfacial friction coefficient by 23%. Using enhanced-sampling simulations, we found that the free-energy landscape of a water monomer is more corrugated on polarizable graphene compared to the non-polarizable model. Quantitative analysis of these landscapes reveals that the friction increase caused by incorporating explicit polarization arises exclusively from a larger lateral force amplitude, which results directly from enhanced energetic surface corrugation.