Question about the calculation of extracted energy from thermostat

Dear Lammps users,

I want to calculate the thermal conductivity of liquid Argon using NEMD.
Thermostats are applied to the bottom and the top of the liquid Argon atoms
to produce constant temperature gradient. The thermal conductivity can be
achieved by using Fourier's Law. *My question is that i am not sure whether
extracted and injected energy from two different thermostats are calculated
correctly using the following commends* (actually i think the value of
f_heatsoure and f_heatsink are the extracted and injected energy from two
different thermostats). The heat flux q is calculated as half slope of the
energy change with respective to the time and heat transfer area in the
thermostats. But the thermal conductivity I got is 188.8 which is much
higher than 0.18 (correct value).

I would very appreciate it if anyone could give me some advice.

Best regards,


fix heatsource higher1 nvt temp 300 300 100
fix heatsink higher2 nvt temp 90 90 100
thermo_style custom step f_heatsource f_heatsink

The values from the two fixes are what the doc page for fix nvt says
they are. You can look at examples/KAPPA and see scripts
which compute thermal conductivity in this manner. The fact
you are getting an answer 1000x different makes me think
you are not normalizing correctly, e.g. by time steps or time or
frequency of the sampling, or the like.