Dear all,

I have done a lot of simulations of thermal conductivity in carbon nanostructures using 3 methods using both LAMMPS (airebo potential) and my own MD simulator (Brenner Potential).

- Fixed-temperature reservoir with rigid boundary
- Muller Plathe with periodic boundaries
- Green Kubo (LAMMPS heat/flux), using only the z component of the conductivity vector.

My own simulator did not have Green-Kubo implemented, so I am very interested in using LAMMPS for my work.

My results using all 3 methods and the 2 potentials/simulators all show qualitatively similar results (300-400 W/m-K for a (10,10) single-walled nanotube @300K).

I was wondering if it seems reasonable that the Green Kubo method would have similar results. I had expected a more accurate result because it is using the autocorrelation of velocity over all atoms in the simulation at a constant temperature.

I had a lot of trouble choosing an appropriate correlation length because it seems to be unstable depending on the seed used for velocity calculation. I ended up getting fairly stable results with ~25 ps, but I am testing further just to make sure it is actually stable. Another email on this list from a couple years ago expressed similar problems up to about 500 ps correlation length.

Has anyone had experience relating the various methods of determining thermal conductivity using NEMD and EMD. I would like to get an idea of what I might expect because I am less familiar with the Green-Kubo formalism at this time. Of course, the complexity here may be a result of using the non-bonded interaction of Airebo or the 1-dimensionality of the conductor. If you have any thoughts I would appreciate the discussion.

Cheers,

Derek Thomas