We report the use of molecular dynamics to identify from equilibrium thermal fluctuations the hydrodynamic modes in a fluid confined by solid walls, thereby extending the application of the fluctuation-dissipation theorem to yield not only the accurate location of the hydrodynamic boundary at the molecular scale, but also the relevant parameter value(s) for the description of the macroscopic boundary condition. Results on two examples are presented to illustrate the application of this approach.
*Work done in collaboration with Shuyu Chen, Han Wang, and Tiezheng Qian