heat flux thermal conductivity (stress term)

Dear Steve and users,

I simply tested the example given in lammps(solid Ar conductivity calculation, http://lammps.sandia.gov/doc/compute_heat_flux.html) with two different variations on computer myStress line.

  1. I removed virial to just ONLY NULL as an option. The final conductivity came out different, 0.4528 compared to with viral term, i.e., NULL virial as options. Basically, my question is how does Lammps calculate the stress term without having any terms for stress? Is this zero or something else?

  2. I used the system temperature (solid Ar temperature) as temp ID to compare with the results with NULL. The thermal results are the same. Now, I thought that NULL could make some difference as the part of the stress term is related to kinetic energy, but it turns out that NULL does not make any difference. Do you have any ideas why?

Thanks, Gisuk.

I think the doc page is pretty clear on these Qs.

If you use just NULL, you get KE + virial = all terms in the eq,

and a default temperature compute is used for the KE term

if you use NULL virial, you get just the virial terms in the eq

(no KE, so it won’t matter if you use NULL of a compute ID for temp)

if you use an ID for compute temp in place of NULL, it

will be the same as NULL, since NULL uses compute temp

The only reason to specify a temperature compute is to

use one that subtracts a bias to give atomic thermal

veloctiies - e.g. compute temp/com or temp/partial