[lammps-users] Thermal Conductivity Calculation

Dear All,

I have lammps 29Sep21 installed.

I’m trying to calculate the thermal conductivity of my nanofluid using the Green-Kubo method.

However, I’m getting a really different result than expected compared to the paper I’m trying to reproduce.

It should be around 0.25 W/m.k but I’m getting 0.006317 W/m.k

The result of the calculation is printed on the last line gives me this “average conductivity: 0.00631711839554993[W/mK] @ 300 K, 0.00225303284455429 /A^3”

I think it has something to do with units for my side but I have checked and can’t find anything.

Can you please help explain to me what I am doing wrong?

My input script is as follows:

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log.lammps (390 KB)

Hi,

Can someone please help me with the email below?

Best regards,
Yunes Salman

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Not really with the Green-Kubo stuff, but your LJ cutoff looks awfully short with 2.5 angstrom?
Where did you get it and the other LJ force field parameters from?
Before simulating the hybrid system, I suggest you validate that you get the ethylene glycol subsystem correctly on its own. There should be plenty of simulation data to compare to in the published literature.

This is generally good MD simulation practice that if you don’t get expected results for a complex system, you try and confirm individual parts first and independently. That will also help with finding proper settings for your GK calculations.

Axel.

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Also, for that kind of molecule, I would have expected to see two different types of hydrogen atoms. There is quite a difference between those connected to carbon and those connected to oxygen and those tend to have different parameters and partial charges (you have the latter, but not the former; is that correct for the force field you have chosen?).

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Dear Yunes,
Did you check the convergence of the heat flux autocorrelation function?

Chamara Somarathna

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