[lammps-users] Periodic Boundary conditions(PBC)

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1

Hello Steve,

If you apply PBC for a Nanotube (say 10nm long) in axial direction and evaluate thermall conductivity by using fix/heat or fix/ thermal conductivity by measuring the temperature gradient, will the resulting thermal cond’ty be the cond’ty of 10nm long tube or for just 5nm long?? (Because if u apply PBC and starts adding & removing heat flux using any of the above commands in PBC, the source & sink are seprated by only half of the length and the linear temp profile is also observed only on one half of the whole length).

Also, I want to make sure that if you apply fix heat command to nanotube with fixed Bound’ry cond’s , in calculating K we need not require a factor of 2 in denominator. Or does the program takes care of it(the factor of 2) based on the boundary conditions specified ??

Thanks
Ajit

2

If you read the Muller-Plathe papers for thermal cond and viscosity
(cited on LAMMPS doc pages for fixes by those names), you'll
see they discuss/include the factor of 2. LAMMPS doesn't compute
that, it just computes fluxes, so you have to use the results
appropriately.

Steve