Parameter-free dissipation in simulated sliding friction

Nonequilibrium molecular-dynamics simulations, of crucial importance in sliding friction, are hampered by arbitrariness and uncertainties in the way Joule heat is removed. We implement in a realistic frictional simulation a parameter-free, non-Markovian, stochastic dynamics, which, as expected from theory, absorbs Joule heat precisely as a semi-infinite harmonic substrate would. Simulating stick-slip friction of a slider over a two-dimensional Lennard-Jones solid, we compare our virtually exact frictional results with approximate ones from commonly adopted empirical dissipation schemes. While the latter are generally in serious error, we show that the exact results can be closely reproduced by a viscous Langevin dissipation at the boundary layer, once the backreflected frictional energy is variationally optimized.