  Understanding the physics of a three-phase contact line between gas, liquid,
and solid is important for numerous applications. At the macroscale, the
three-phase contact line response to an external force action is often
characterized by a contact angle hysteresis, and several models are presented
in the literature for its description. Yet, there is still a need for more
information about such model applications at the nanoscale. In this study, a
molecular dynamics approach was used to investigate the shape of a liquid
droplet under an external force for different wetting regimes. In addition, an
analytic model for describing the droplet shape was developed. It gives us the
possibility to evaluate the receding and advancing wetting angle accurately.
With our modeling, we found that the interplay between capillary forces and
viscous forces is crucial to characterize the droplet shape at the nanoscale.
In this frame, the importance of the rolling movement of the interface between
liquid and vapor was pointed out. We also demonstrate that in the range of the
external forces when capillary forces are most significant compared to others,
hysteresis is well described by the macroscale Cox-Voinov model.
