On the equivalence of nonequilibrium and equilibrium measurements of slip in molecular dynamics simulations

We show that nonequilibrium and equilibrium measurements of slip are consistent, provided the hydrodynamic wall location associated with the equilibrium measurement is properly taken into account. The latter is a strong function of the fluid state and wall-fluid interaction and cannot be neglected as it typically has been. Our results are based on an alternative approach for calculating the hydrodynamic wall location which alleviates most of the difficulties associated with its calculation via a Green-Kubo integral that appear to have contributed to its neglect. Extensive molecular dynamics simulations are used to validate our approach including a model for calculating the slip length that does not involve a Green-Kubo integral.

Automated summary

We demonstrate the consistency between nonequilibrium and equilibrium measurements of slip by properly considering the hydrodynamic wall location associated with equilibrium measurement. The neglect of this location, which is strongly influenced by fluid state and wall-fluid interaction, has been addressed in our alternative approach. Extensive molecular dynamics simulations are conducted to validate our method, which includes a slip length calculation model without using a Green-Kubo integral.