Reproducibility of atomistic friction computer experiments: a molecular dynamics simulation study

S Stephan and M Dyga and IA Alhafez and J Lenhard and HM Urbassek and H Hasse, MOLECULAR SIMULATION, 47, 1509-1521 (2021).

DOI: 10.1080/08927022.2021.1987430

The elementary processes of friction in contact processes of two solid bodies occur on the nanoscale and are difficult to study experimentally. Therefore, molecular dynamics simulations are often used for their elucidation. In these studies, usually, only a single simulation is carried out for each scenario and the resulting observables are evaluated. In the present work, the reliability and reproducibility of measured observables from such nanoscopic contact process simulations are assessed by means of their statistical uncertainties. Therefore, the computer experiment is carried out not only once, but it is repeated eight times, with individual runs that only differ in the initial thermal motion. This set of replicas enables an assessment of observations for distinguishing reproducible physical phenomena from stochastic coincidence. In this way, a dry and a lubricated nanoscale scratching process were studied, in which a cylindrical indenter carried out two sequential movements: it first penetrates a substrate vertically and then scratches laterally, which causes elastic and plastic deformation of the substrate. In the lubricated case, the indenter was fully immersed in the fluid. Substrate, indenter, and fluid were described by suitably parametrised Lennard-Jones potentials. Various mechanical and thermodynamic process properties were monitored in all simulation runs. The results are compared and evaluated statistically.

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