Dear Users,

I want to measure thermal conductivity of Ar. For the convergence test I did several simulations with

cell size = 4x4x4unit cell(fcc) ,Temperature=10K

Question: 1) when timestep=5 fs

correlation length=200

and sample interval=100(so the correlation time here is 5x200x100fs=100ps)

then the value of tensor components(k11,k22,k33) of thermal conductivity are near about 1.9W/mK which is not equal to the already published value(~2.5W/mK)

But when timestep=10 fs

correlation length=200

and sample interval=50(so the correlation time here is 10x200x50fs=100ps)

then the value of tensor components(k11,k22,k33) of thermal conductivity are near about 2W/mK up to 4,300,000 steps(total steps is 10,000,000) but after that they

increase exponentially !!!

Could you suggest me about the reason behind that strange increment and how to get rid of that problem???

Question: 2) In my script the “thermo” command prints tensor components(k11,k22,k33) of thermal conductivity in log file along with other some variables and also for convenience

I have saved those components in a separate .txt file. Surprisingly the values read by log file and .txt file are not same !!!

Please help me by giving some suggestion.

I am attaching my input script files and output log files corresponds to above two questions

Question: 3) What is exact method to check the convergence since for different combination of “timestep”,“correlation length” and “sample interval” I am getting different values of

thermal conductivity along with problem which I face in Question: 1 ??

Thanks & Regards

Amal

in.therm_Ar_GK_5fs (1.89 KB)

in.therm_Ar_GK_10fs (1.89 KB)

log.thermoAr_GK_5fs (76.6 KB)

log.thermoAr_GK_10fs (148 KB)