Building the bridge from atomistic to stochastic modelling of nanoscale friction phenomena

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Direct molecular dynamic simulation of a nanoscale object involves numerical integration of the equations of motion for all its atoms. This approach is exact, but it has severe size and time-scale limitations. Stochastic modelling overcomes these limitations by focusing on only a small subset of the relevant degrees of freedom, termed "the system". The remaining large number of the irrelevant ones, denoted as "the heat bath", are not simulated explicitly, but taken into account by (i) renormalizing the forces acting on and between the system coordinates, (ii) including dissipative forces describing the energy transfer from the system into the heat bath, and (iii) introducing random forces describing the effect of thermal motion of the heat-bath atoms on the system.