Approaches to Evaluating Transport Properties
Need a non-equilibrium condition
Method 1: Establish a non-equilibrium steady state
- “Non-equilibrium molecular dynamics” NEMD
- Requires continuous addition and removal of conserved quantities
- Usually involves application of work, so must apply thermostat
- Only one transport property measured at a time
- Gives good statistics (high “signal-to-noise ratio”)
- Requires extrapolation to “linear regime”
Method 2: Rely on natural fluctuations
- Any given configuration has natural anisotropy of mass, momentum, energy
- Observe how these natural fluctuations dissipate
- All transport properties measurable at once
- Poor signal-to-noise ratio