# ZnO thermal conductivity

Dear lammps users：
I have some questions on ZnO thermal conductivity calculation，The fix heat/flux and fix thermal/conductivity command were selected to calculating the ZnO thermal conductivity.
1.fix heat/flux
I wrote the input file like the manual (http://lammps.sandia.gov/doc/compute_heat_flux.html), the average thermal conductivity of ZnO(Model: x 5.0nm y 4.8nm z 5.3nm) is about ~50W/mk. The thermal conductivity-m curve you can see the fig 1 in the attachment.
2.thermal/conductivity
The periodic boundary wurtzite-type ZnO was selected to calculating thermal conductivity in x y z direction 2.8nm 2.9nm 15.7nm respectively。The main command as following：
fix temp_profile all ave/spatial 1 100000 100000 z lower 1.0 v_temp file temp.profile units lattice #YL for test
fix heat_swap all thermal/conductivity 10 z 60
fix e_exchange all ave/time 10 1 100000 f_heat_swap file e_exchange.dat
fix accumu_thermalK_out all ave/time 10 1 100000 v_accumu_thermalK file thermal_conductivity.dat
I used this “variable accumu_thermalK equal f_e_exchange*{ev2J}/(2*0.001*{N}{ps2s}*{Ox}{Oy}*{An2m}f_delta_out)(\${Oz}/60.0*26.0)” variable command to calculating it.
timestep 0.001
N step
Is it right（this variable to calculate the thermal conductivity）?
Temperature gradient is linear in the fig 2 (in the attachment). the average thermal conductivity is about 5W/mk.

Now, Two kinds of method to calculate the thermal conductivity of why have so big difference(The two methods with the same potential)?

Dear lammps users：
I have some questions on ZnO thermal conductivity calculation，The fix
heat/flux and fix thermal/conductivity command were selected to calculating
the ZnO thermal conductivity.

[ ...]

Now, Two kinds of method to calculate the thermal conductivity of why
have so big difference(The two methods with the same potential)?

please search the mailing list archive for previous discussions on the
topic (it is a frequently recurring one). different methods have
different requirements to work well and different statistical
convergence. any property that is not instantaneous is subject to that
and any complex calculation can have many factors that influence its
systematic errors.

axel.